UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934

                                (Amendment No. ________)*

                               BSquare Corporation
--------------------------------------------------------------------------------
                                (Name of Issuer)

                                  Common Stock
--------------------------------------------------------------------------------
                         (Title of Class of Securities)


                                    11776U102
                  ---------------------------------------------
                                 (CUSIP Number)



                                December 31, 2001
         --------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)


            Check the appropriate box to designate the rule pursuant
                        to which this Schedule is filed:

                                [x]  Rule 13d-1(b)
                                [_]  Rule 13d-1(c)
                                [_]  Rule 13d-1(d)



*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).

                               Page 1 of 10 Pages



-----------------------------                         ------------------------
 CUSIP No.  11776U102                  13G             Page 2 of 10 Pages
           ---------------
-----------------------------                         ------------------------
------------------------------------------------------------------------------
      NAME OF REPORTING PERSON
 1    S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

        Liberty Wanger Asset Management, L.P. 36-3820584
------------------------------------------------------------------------------
      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
 2                                                              (a) [_]
        Not Applicable                                          (b) [_]
------------------------------------------------------------------------------
      SEC USE ONLY
 3

------------------------------------------------------------------------------
      CITIZENSHIP OR PLACE OF ORGANIZATION
 4
        Delaware
------------------------------------------------------------------------------
                          SOLE VOTING POWER
                     5
     NUMBER OF              None
      SHARES       -----------------------------------------------------------
                          SHARED VOTING POWER
   BENEFICIALLY      6
     OWNED BY               3,400,000
                   -----------------------------------------------------------
       EACH               SOLE DISPOSITIVE POWER
                     7
    REPORTING               None
      PERSON       -----------------------------------------------------------
                          SHARED DISPOSITIVE POWER
       WITH          8
                            3,400,000
------------------------------------------------------------------------------
      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
 9
        3,400,000
------------------------------------------------------------------------------
      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
10
        Not Applicable                                              [_]
------------------------------------------------------------------------------
      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
11
        9.9%
------------------------------------------------------------------------------
      TYPE OF REPORTING PERSON*
12
        IA
------------------------------------------------------------------------------
                      *SEE INSTRUCTIONS BEFORE FILLING OUT!



-----------------------------                         ------------------------
 CUSIP No.  11776U102                  13G             Page 3 of 10 Pages
           ---------------
-----------------------------                         ------------------------
------------------------------------------------------------------------------
      NAME OF REPORTING PERSON
 1    S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

        WAM Acquisition GP, Inc.
------------------------------------------------------------------------------
      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
 2                                                              (a) [_]
        Not Applicable                                          (b) [_]
------------------------------------------------------------------------------
      SEC USE ONLY
 3

------------------------------------------------------------------------------
      CITIZENSHIP OR PLACE OF ORGANIZATION
 4
        Delaware
------------------------------------------------------------------------------
                          SOLE VOTING POWER
                     5
     NUMBER OF              None
      SHARES       -----------------------------------------------------------
                          SHARED VOTING POWER
   BENEFICIALLY      6
     OWNED BY               3,400,000
                   -----------------------------------------------------------
       EACH               SOLE DISPOSITIVE POWER
                     7
    REPORTING               None
      PERSON       -----------------------------------------------------------
                          SHARED DISPOSITIVE POWER
       WITH          8
                            3,400,000
------------------------------------------------------------------------------
      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
 9
        3,400,000
------------------------------------------------------------------------------
      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
10
        Not Applicable                                              [_]
------------------------------------------------------------------------------
      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
11
        9.9%
------------------------------------------------------------------------------
      TYPE OF REPORTING PERSON*
12
        CO
------------------------------------------------------------------------------
                      *SEE INSTRUCTIONS BEFORE FILLING OUT!



-------------------------                              -------------------------
 CUSIP NO.   11776U102                 13G               Page 4 of 10 Pages
           -------------
-------------------------                              -------------------------
--------------------------------------------------------------------------------
      NAME OF REPORTING PERSON
 1    S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

        Liberty Acorn Trust
------------------------------------------------------------------------------
      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
 2                                                              (a) [_]
        Not Applicable                                          (b) [_]
------------------------------------------------------------------------------
      SEC USE ONLY
 3
------------------------------------------------------------------------------
      CITIZENSHIP OR PLACE OF ORGANIZATION
 4
      Massachusetts
------------------------------------------------------------------------------
                          SOLE VOTING POWER
                     5
     NUMBER OF              None
      SHARES       -----------------------------------------------------------
                          SHARED VOTING POWER
   BENEFICIALLY      6
     OWNED BY               3,200,000
                   -----------------------------------------------------------
       EACH               SOLE DISPOSITIVE POWER
                     7
    REPORTING               None
      PERSON       -----------------------------------------------------------
                          SHARED DISPOSITIVE POWER
       WITH          8
                            3,200,000
------------------------------------------------------------------------------
      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
 9
        3,200,000
------------------------------------------------------------------------------
      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
10

        Not Applicble                                               [_]
------------------------------------------------------------------------------
      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
11
        9.3%
------------------------------------------------------------------------------
      TYPE OF REPORTING PERSON*
12
        IV
------------------------------------------------------------------------------



Item 1(a)      Name of Issuer:

                    BSquare Corporation

Item 1(b)      Address of Issuer's Principal Executive Offices:

                    3150 139/th/ Avenue SE, Suite 500
                    Bellevue, WA 98005

Item 2(a)      Name of Person Filing:

                    Liberty Wanger Asset Management, L.P. ("WAM")
                    WAM Acquisition GP, Inc., the general partner of WAM
                     ("WAM GP")
                    Liberty Acorn Trust ("Acorn")

Item 2(b)      Address of Principal Business Office:

                    WAM, WAM GP and Acorn are all located at:

                    227 West Monroe Street, Suite 3000
                    Chicago, Illinois  60606

Item 2(c)      Citizenship:

                    WAM is a Delaware limited partnership; WAM GP is a Delaware
                    corporation; and Acorn is a Massachusetts business trust.

Item 2(d)      Title of Class of Securities:

                    Common Stock

Item 2(e)      CUSIP Number:

                    11776U102

Item 3         Type of Person:

                    (d)  Acorn is an Investment Company under section 8 of the
                         Investment Company Act.

                    (e)  WAM is an Investment Adviser registered under section
                         203 of the Investment Advisers Act of 1940; WAM GP is
                         the General Partner of the Investment Adviser.

                               Page 5 of 10 Pages



Item 4         Ownership (at December 31, 2001):

                    (a)  Amount owned "beneficially" within the meaning of rule
                         13d-3:

                         3,400,000

                    (b)  Percent of class:

                         9.9 % (based on 34,493,524 shares outstanding as of
                         November 2, 2001)

                    (c)  Number of shares as to which such person has:

                             (i)  sole power to vote or to direct the vote: none
                            (ii)  shared power to vote or to direct the
                                  vote:  3,400,000
                           (iii)  sole power to dispose or to direct the
                                  disposition of:  none
                            (iv)  shared power to dispose or to direct
                                  disposition of:  3,400,000

Item 5         Ownership of Five Percent or Less of a Class:

                    Not Applicable

Item 6         Ownership of More than Five Percent on Behalf of Another Person:

                    The shares reported herein have been acquired on behalf of
                    discretionary clients of WAM, including Acorn. Persons other
                    than WAM and WAM GP are entitled to receive all dividends
                    from, and proceeds from the sale of, those shares. Acorn is
                    the only such person known to be entitled to all dividends
                    from, and all proceeds from the sale of, shares reported
                    herein to the extent of more than 5% of the class.

Item 7         Identification and Classification of the Subsidiary Which
               Acquired the Security Being Reported on by the Parent Holding
               Company:

                    Not Applicable

Item 8         Identification and Classification of Members of the Group:

                    Not Applicable

Item 9         Notice of Dissolution of Group:

                    Not Applicable

                               Page 6 of 10 Pages



Item 10                    Certification:

                                    By signing below I certify that, to the best
                           of my knowledge and belief, the securities referred
                           to above were acquired and are held in the ordinary
                           course of business and were not acquired and are not
                           held for the purpose of or with the effect of
                           changing or influencing the control of the issuer of
                           the securities and were not acquired and are not held
                           in connection with or as a participant in any
                           transaction having that purpose or effect.

                                Page 7 of Pages



                                    Signature
                                    ---------

         After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

Date:  February 14, 2002


                           The undersigned corporation, on the date above
                           written, agrees and consents to the joint filing on
                           its behalf of this Schedule 13G in connection with
                           its beneficial ownership of the security reported
                           herein.

                                   WAM Acquisition GP, Inc.
                                       for itself and as general partner of
                                       LIBERTY WANGER ASSET MANAGEMENT, L.P.



                                   By:  /s/ Bruce H. Lauer
                                        ----------------------------------------
                                            Bruce H. Lauer
                                            Senior Vice President and Secretary

                           The undersigned corporation, on the date above
                           written, agrees and consents to the joint filing on
                           its behalf of this Schedule 13G in connection with
                           its beneficial ownership of the security reported
                           herein.

                                   LIBERTY ACORN TRUST



                                   By:  /s/ Bruce H. Lauer
                                        ----------------------------------------
                                            Bruce H. Lauer
                                            Vice President, Treasurer and
                                            Secretary

                               Page 8 of 10 Pages



                                  Exhibit Index
                                  -------------

Exhibit 1     Joint Filing Agreement dated as of February 14, 2002 by and among
              Liberty Wanger Asset Management, L.P., WAM Acquisition GP, Inc.
              and Liberty Acorn Trust

                               Page 9 of 10 Pages



                                                                       EXHIBIT 1

                             JOINT FILING AGREEMENT

         The undersigned hereby agree to the joint filing of the Schedule 13G to
which this Agreement is attached.


                  Dated:  February 14, 2002


                                WAM Acquisition GP, Inc.
                                    for itself and as general partner of
                                    LIBERTY WANGER ASSET MANAGEMENT, L.P.



                                By:  /s/ Bruce H. Lauer
                                     -------------------------------------------
                                         Bruce H. Lauer
                                         Senior Vice President and Secretary

                                LIBERTY ACORN TRUST



                                By:  /s/ Bruce H. Lauer
                                     -------------------------------------------
                                         Bruce H. Lauer
                                         Vice President, Treasurer and
                                         Secretary

                              Page 10 of 10 Pages