UNITED STATES
                       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 27, 2005

                        MainSource Financial Group, Inc.
             (Exact name of registrant as specified in its charter)


      Indiana                           0-12422                  35-1562245
State or Other Jurisdiction of     Commission File No.        I.R.S. Employer
Incorporation or Organization                             Identification Number


                               201 North Broadway
                            Greensburg, Indiana 47240
                    (Address of principal executive offices)

                                 (812) 663-0157
                         (Registrant's Telephone Number,
                              Including Area Code)

                                       N/A
          (Former Name or Former Address, if Changed Since Last Report)

     Check the  appropriate  box below if the Form 8-K  filing  is  intended  to
simultaneously  satisfy the filing obligation of the registrant under any of the
following provisions:

  [ ] Written communications pursuant to Rule 425 under the Securities Act
      (17 CFR 230.425)
  [ ] Soliciting material pursuant to Rule 14a-12 under the Exchange Act
      (17 CFR 240.14a-12)
  [ ] Pre-commencement communications pursuant to Rule 14d-2(b) under the
      Exchange Act (17 CFR 240.14d-2(b))
  [ ] Pre-commencement communications pursuant to Rule 13e-4(c) under the
      Exchange Act(17 CFR 240.13e-4(c))





Item 1.01.     Entry into a Material Definitive Agreement

Acceleration of Options

Effective  December  27,  2005,  the  Compensation  Committee  of the  Board  of
Directors of MainSource  Financial Group,  Inc.  ("MainSource")  accelerated the
vesting  of  all   outstanding,   "out-of-the-money",   unvested  stock  options
("Options") awarded to recipients under its 2003 Stock Option Plan. The decision
to accelerate  the vesting was made  primarily to reduce  non-cash  compensation
expense that  MainSource  would have recorded in its income  statement in future
periods upon the adoption of Financial  Accounting Standards Board Statement No.
123R  (Share-Based  Payment) in January  2006.  These  Options  previously  were
awarded to executive officers and employees.

The Compensation  Committee believed it was in the best interest of MainSource's
shareholders   to   accelerate   the  vesting  of  these  Options  to  eliminate
compensation  expense in future periods. As a result of this action,  Options to
purchase up to 112,321  shares of common stock become  exercisable  immediately.
Without the  acceleration,  the Options  would have vested on dates ranging from
December 31, 2005 to December 31, 2008.

Since  MainSource  currently  accounts for its stock options in accordance  with
Accounting  Principles  Board  Opinion No. 25,  Accounting  for Stock  Issued to
Employees ("APB No. 25"), it will report its estimates of the eliminated  future
compensation  expense related to the affected Options in its fourth quarter 2005
financial statements as a pro-forma disclosure.



                                   SIGNATURES

     Pursuant to the  requirements  of the Securities  Exchange Act of 1934, the
registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned, thereunto duly authorized.

                                     MAINSOURCE FINANCIAL GROUP, INC.

Date:    January 3, 2006             By:  /s/ James L. Saner, Sr.
                                          -----------------------
                                          James L. Saner, Sr.
                                          President and Chief Executive Officer