content: <PAGE>
  
                         SECURITIES AND EXCHANGE COMMISSION
                               Washington, D.C. 20549
  
  
                                      FORM 8-K
  
  
                              Current Report Pursuant
                           to Section 13 or 15(d) of the
                          Securities Exchange Act of 1934
  
        Date of Report (Date of earliest event reported): December 14, 1999
  
  
                                Greater Bay Bancorp
              (Exact name of registrant as specified in its charter)
  
  
  
           California                                           77-0387041
  (State or other jurisdiction of                            (I.R.S. employer
   incorporation or organization)                         identification number)
  
  
                         Commission file number:  0-25034
  
  
                              2860 West Bayshore Road
                            Palo Alto, California 94303
               (Address of principal executive offices and zip code)
  
  
         Registrant's telephone number, including area code: (650) 813-8200
  
  <PAGE>
  
  Item 5.  Other Events.
  
    On December 14, 1999, Greater Bay Bancorp (the "Registrant") entered into an
  Agreement and Plan of Reorganization with Coast Bancorp ("Coast") providing for
  the merger of Coast with and into the Registrant (the "Merger"), subject to the
  terms and conditions therein, including the receipt of all required regulatory
  approvals and the approval of the shareholders of the Registrant and Coast.
  Following consummation of the Merger, Coast Commercial Bank, a wholly owned
  subsidiary of Coast, will become a wholly owned subsidiary of the Registrant.
  
    Included as Exhibit 99.4 of this Current Report on Form 8-K is unaudited pro
  forma condensed combined financial information. The Unaudited Pro Forma
  Condensed Combined Balance Sheet as of September 30, 1999 combines the
  historical consolidated balance sheets of the Registrant, Bay Commercial
  Services ("BCS") (which merged with the Registrant on October 15, 1999), Mt.
  Diablo Bancshares ("MDB") (which signed a definitive agreement on September 15,
  1999 to merge with the Registrant) and Coast, as if all of these mergers had
  been effective on September 30, 1999, after giving effect to certain
  adjustments. These adjustments are based on estimates. The Unaudited Pro Forma
  Condensed Combined Statements of Operations for the nine months ended September
  30, 1999 and 1998 and for the years ended December 31, 1998, 1997 and 1996
  present the combined results of operations of the Registrant, BCS, MDB and Coast
  as if the mergers had been effective at the beginning of each period. No
  assurance can be given when and if the proposed mergers with MDB and Coast will
  be consummated.
  
    The unaudited pro forma condensed combined financial information and
  accompanying notes reflect the application of the pooling of interests method of
  accounting for the mergers.  Under this method of accounting, the recorded
  assets, liabilities, shareholders' equity, income and expenses of the
  Registrant, BCS, MDB and Coast are combined and reflected at their historical
  amounts.
  
    The pro forma combined figures shown in the unaudited pro forma condensed
  combined financial information are simply arithmetical combinations of the
  Registrant's, BCS', MDB's and Coast's separate financial results; you should not
  assume that the Registrant, BCS, MDB and Coast would have achieved the pro forma
  combined results if they had actually been combined during the periods
  presented.
  
    The combined company expects to achieve merger benefits in the form of
  operating cost savings.  The pro forma earnings, which do not reflect any direct
  costs or potential savings which are expected to result from the consolidation
  of the operations of the Registrant, BCS, MDB and Coast, are not indicative of
  the results of future operations.  No assurances can be given with respect to
  the ultimate level of expense savings.
  
  Pro Forma Earnings with Operating Efficiencies
  
       The pro forma condensed combined financial information contained in Exhibit
  99.4 indicates that, for the nine months ended September 30, 1999, the
  Registrant's net earnings per share (1) would have been $1.62, a decline of
  $0.04 from the reported earnings before the mergers with BCS, MDB and Coast.
  However, these pro forma earnings per share do not reflect the operating
  efficiencies that the Registrant has realized in all of its previous mergers. On
  average, the Registrant has realized operating efficiencies from its prior
  mergers in excess of 15% of the operating expenses of the acquired institutions.
  The following table details the impact of applying the Registrant's historical
  percentage of operating efficiencies attained on a pro forma basis to September
  30, 1999 earnings:
  
  <TABLE>
  <CAPTION>
                                                       Operating          Net
                                                       Expenses        Income (1)        EPS (1)
                                                       ---------       ----------        -------
  <S>                                                   <C>            <C>               <C>
   Pro-Forma Net Income Before
    Operating Efficiencies                                               $27,814           $1.62
  
  Operating Expenses:
    Bay Commercial Services                             $ 4,353
    Coast                                               $ 9,884
    Mt. Diablo                                          $ 4,238
                                                        -------
      Total                                             $18,475
                                                        =======
  
    Greater Bay Historical Merger & Acquisition
      Operating Efficiencies                                 15%
  
  Estimated Operating Efficiencies, Gross               $ 2,771
                                                        =======
  
  Estimated Operating Efficiencies, Net of Tax          $ 1,718          $ 1,718           $0.10
                                                        =======         --------         -------
  Adjusted Pro-Forma Net Income After
    Operating Efficiencies                                               $29,532           $1.72
                                                                        ========         =======
  
  
  (1) - Before merger and other related nonrecurring costs and extraordinary items.
  </TABLE>
  
       No assurance can be given that these operating efficiencies will be
  achieved.  Information contained under this caption constitutes "forward-looking
  statements" within the meaning of Section 27A of the Securities Act of 1933, as
  amended, and Section 21E of the Securities Exchange Act of 1934, as amended,
  which involve risks and uncertainties.  The Registrant's actual results may
  differ significantly from the results discussed in these forward-looking
  statements.  Factors that might cause such a difference include but are not
  limited to difficulties in integrating the business of the newly acquired
  institutions, the timing relating to achieving the operating efficiencies,
  economic conditions, competition in the geographic and business areas in which
  the Registrant conducts its operations and government regulation.
  <PAGE>
  
  Item 7.  Financial Statements and Exhibits.
  
  Exhibits
  --------
  
  2     Agreement and Plan of Reorganization, dated as of December 14, 1999, by
        and between Greater Bay Bancorp and Coast Bancorp
  
  10.1  Stock Option Agreement, dated as of December 14, 1999, by and between
        Greater Bay Bancorp and Coast Bancorp
  
  99.1  Press Release dated December 14, 1999 re Coast merger
  
  99.2  Press Release dated December 14, 1999 re dividend declaration
  
  99.3  Press Release dated December 14, 1999 re addition to Nasdaq Financial-100
        Index
  
  99.4  Unaudited Pro Forma Condensed Combined Balance Sheet as of September 30,
        1999 and Unaudited Pro Forma Condensed Combined Statements of Operations
        for the nine months ended September 30, 1999 and 1998 and for the years
        ended December 31, 1998, 1997 and 1996
  <PAGE>
  
                                    SIGNATURES
  
       Pursuant to the requirements of the Securities Exchange Act of 1934, as
  amended, the Registrant has duly caused this report to be signed on its behalf
  by the undersigned hereunto duly authorized.
  
                                       Greater Bay Bancorp
                                       (Registrant)
  
  
  
  Dated: December 15, 1999             By: /s/ Linda M. Iannone
                                           --------------------
                                           Linda M. Iannone
                                           Senior Vice President and General
                                           Counsel
  <PAGE>
  
                                   Exhibit Index
                                   -------------
  
  2     Agreement and Plan of Reorganization, dated as of December 14, 1999, by
        and between Greater Bay Bancorp and Coast Bancorp
  
  10.1  Stock Option Agreement, dated as of December 14, 1999, by and between
        Greater Bay Bancorp and Coast Bancorp
  
  99.1  Press Release dated December 14, 1999 re Coast merger
  
  99.2  Press Release dated December 14, 1999 re dividend declaration
  
  99.3  Press Release dated December 14, 1999 re addition to Nasdaq Financial-100
        Index
  
  99.4  Unaudited Pro Forma Condensed Combined Balance Sheet as of September 30,
        1999 and Unaudited Pro Forma Condensed Combined Statements of Operations
        for the nine months ended September 30, 1999 and 1998 and for the years
        ended December 31, 1998, 1997 and 1996
metadata_documents: [{"type": "8-K", "sequence": "1", "description": "FORM 8-K", "secsgml_size_bytes": 9616}]
metadata_filer: {"company-data": {"conformed-name": "GREATER BAY BANCORP", "cik": "0000775473", "assigned-sic": "6021", "irs-number": "770387041", "state-of-incorporation": "CA", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "000-25034", "film-number": "99776159"}, "business-address": {"street1": "2860 WEST BAYSHORE ROAD", "city": "PALO ALTO", "state": "CA", "zip": "94303", "phone": "4153751555"}, "mail-address": {"street1": "2860 BAYSHORE ROAD", "street2": "420 COWPER ST", "city": "PALO ALTO", "state": "CA", "zip": "943011504"}, "former-company": [{"former-conformed-name": "MID PENINSULA BANCORP", "date-changed": "19941031"}, {"former-conformed-name": "SAN MATEO COUNTY BANCORP", "date-changed": "19920703"}]}
text: SECURITIES AND EXCHANGE COMMISSION
                               Washington, D.C. 20549
  
                                      FORM 8-K
  
                              Current Report Pursuant
                           to Section 13 or 15(d) of the
                          Securities Exchange Act of 1934
  
        Date of Report (Date of earliest event reported): December 14, 1999
  
                                Greater Bay Bancorp
              (Exact name of registrant as specified in its charter)
  
           California                                           77-0387041
  (State or other jurisdiction of                            (I.R.S. employer
   incorporation or organization)                         identification number)
  
                         Commission file number:  0-25034
  
                              2860 West Bayshore Road
                            Palo Alto, California 94303
               (Address of principal executive offices and zip code)
  
         Registrant's telephone number, including area code: (650) 813-8200
  Item 5.  Other Events.
  
    On December 14, 1999, Greater Bay Bancorp (the "Registrant") entered into an
  Agreement and Plan of Reorganization with Coast Bancorp ("Coast") providing for
  the merger of Coast with and into the Registrant (the "Merger"), subject to the
  terms and conditions therein, including the receipt of all required regulatory
  approvals and the approval of the shareholders of the Registrant and Coast.
  Following consummation of the Merger, Coast Commercial Bank, a wholly owned
  subsidiary of Coast, will become a wholly owned subsidiary of the Registrant.
  
    Included as Exhibit 99.4 of this Current Report on Form 8-K is unaudited pro
  forma condensed combined financial information. The Unaudited Pro Forma
  Condensed Combined Balance Sheet as of September 30, 1999 combines the
  historical consolidated balance sheets of the Registrant, Bay Commercial
  Services ("BCS") (which merged with the Registrant on October 15, 1999), Mt.
  Diablo Bancshares ("MDB") (which signed a definitive agreement on September 15,
  1999 to merge with the Registrant) and Coast, as if all of these mergers had
  been effective on September 30, 1999, after giving effect to certain
  adjustments. These adjustments are based on estimates. The Unaudited Pro Forma
  Condensed Combined Statements of Operations for the nine months ended September
  30, 1999 and 1998 and for the years ended December 31, 1998, 1997 and 1996
  present the combined results of operations of the Registrant, BCS, MDB and Coast
  as if the mergers had been effective at the beginning of each period. No
  assurance can be given when and if the proposed mergers with MDB and Coast will
  be consummated.
  
    The unaudited pro forma condensed combined financial information and
  accompanying notes reflect the application of the pooling of interests method of
  accounting for the mergers.  Under this method of accounting, the recorded
  assets, liabilities, shareholders' equity, income and expenses of the
  Registrant, BCS, MDB and Coast are combined and reflected at their historical
  amounts.
  
    The pro forma combined figures shown in the unaudited pro forma condensed
  combined financial information are simply arithmetical combinations of the
  Registrant's, BCS', MDB's and Coast's separate financial results; you should not
  assume that the Registrant, BCS, MDB and Coast would have achieved the pro forma
  combined results if they had actually been combined during the periods
  presented.
  
    The combined company expects to achieve merger benefits in the form of
  operating cost savings.  The pro forma earnings, which do not reflect any direct
  costs or potential savings which are expected to result from the consolidation
  of the operations of the Registrant, BCS, MDB and Coast, are not indicative of
  the results of future operations.  No assurances can be given with respect to
  the ultimate level of expense savings.
  
  Pro Forma Earnings with Operating Efficiencies
  
       The pro forma condensed combined financial information contained in Exhibit
  99.4 indicates that, for the nine months ended September 30, 1999, the
  Registrant's net earnings per share (1) would have been $1.62, a decline of
  $0.04 from the reported earnings before the mergers with BCS, MDB and Coast.
  However, these pro forma earnings per share do not reflect the operating
  efficiencies that the Registrant has realized in all of its previous mergers. On
  average, the Registrant has realized operating efficiencies from its prior
  mergers in excess of 15% of the operating expenses of the acquired institutions.
  The following table details the impact of applying the Registrant's historical
  percentage of operating efficiencies attained on a pro forma basis to September
  30, 1999 earnings:
  Operating          Net
                                                       Expenses        Income (1)        EPS (1)
                                                       ---------       ----------        -------
  Pro-Forma Net Income Before
    Operating Efficiencies                                               $27,814           $1.62
  
  Operating Expenses:
    Bay Commercial Services                             $ 4,353
    Coast                                               $ 9,884
    Mt. Diablo                                          $ 4,238
                                                        -------
      Total                                             $18,475
                                                        =======
  
    Greater Bay Historical Merger & Acquisition
      Operating Efficiencies                                 15%
  
  Estimated Operating Efficiencies, Gross               $ 2,771
                                                        =======
  
  Estimated Operating Efficiencies, Net of Tax          $ 1,718          $ 1,718           $0.10
                                                        =======         --------         -------
  Adjusted Pro-Forma Net Income After
    Operating Efficiencies                                               $29,532           $1.72
                                                                        ========         =======
  
  (1) - Before merger and other related nonrecurring costs and extraordinary items.
  No assurance can be given that these operating efficiencies will be
  achieved.  Information contained under this caption constitutes "forward-looking
  statements" within the meaning of Section 27A of the Securities Act of 1933, as
  amended, and Section 21E of the Securities Exchange Act of 1934, as amended,
  which involve risks and uncertainties.  The Registrant's actual results may
  differ significantly from the results discussed in these forward-looking
  statements.  Factors that might cause such a difference include but are not
  limited to difficulties in integrating the business of the newly acquired
  institutions, the timing relating to achieving the operating efficiencies,
  economic conditions, competition in the geographic and business areas in which
  the Registrant conducts its operations and government regulation.
  Item 7.  Financial Statements and Exhibits.
  
  Exhibits
  --------
  
  2     Agreement and Plan of Reorganization, dated as of December 14, 1999, by
        and between Greater Bay Bancorp and Coast Bancorp
  
  10.1  Stock Option Agreement, dated as of December 14, 1999, by and between
        Greater Bay Bancorp and Coast Bancorp
  
  99.1  Press Release dated December 14, 1999 re Coast merger
  
  99.2  Press Release dated December 14, 1999 re dividend declaration
  
  99.3  Press Release dated December 14, 1999 re addition to Nasdaq Financial-100
        Index
  
  99.4  Unaudited Pro Forma Condensed Combined Balance Sheet as of September 30,
        1999 and Unaudited Pro Forma Condensed Combined Statements of Operations
        for the nine months ended September 30, 1999 and 1998 and for the years
        ended December 31, 1998, 1997 and 1996
  SIGNATURES
  
       Pursuant to the requirements of the Securities Exchange Act of 1934, as
  amended, the Registrant has duly caused this report to be signed on its behalf
  by the undersigned hereunto duly authorized.
  
                                       Greater Bay Bancorp
                                       (Registrant)
  
  Dated: December 15, 1999             By: /s/ Linda M. Iannone
                                           --------------------
                                           Linda M. Iannone
                                           Senior Vice President and General
                                           Counsel
  Exhibit Index
                                   -------------
  
  2     Agreement and Plan of Reorganization, dated as of December 14, 1999, by
        and between Greater Bay Bancorp and Coast Bancorp
  
  10.1  Stock Option Agreement, dated as of December 14, 1999, by and between
        Greater Bay Bancorp and Coast Bancorp
  
  99.1  Press Release dated December 14, 1999 re Coast merger
  
  99.2  Press Release dated December 14, 1999 re dividend declaration
  
  99.3  Press Release dated December 14, 1999 re addition to Nasdaq Financial-100
        Index
  
  99.4  Unaudited Pro Forma Condensed Combined Balance Sheet as of September 30,
        1999 and Unaudited Pro Forma Condensed Combined Statements of Operations
        for the nine months ended September 30, 1999 and 1998 and for the years
        ended December 31, 1998, 1997 and 1996