MILLER, NASH, WIENER, HAGER & CARLSEN LLP
                                ATTORNEYS AT LAW
                            3500 U. S. BANCORP TOWER
                              111 S.W. FIFTH AVENUE
                           PORTLAND, OREGON 97204-3699
                            TELEPHONE (503) 224-5858
                            FACSIMILE (503) 224-0155










                                  April 2, 1997




Barrett Business Services, Inc.
4724 S.W. Macadam Avenue
Portland, Oregon  97201

                   Subject:   Registration Statement on Form S-3
                              157,443 Shares of Common Stock

Gentlemen:

                  Reference  is made to the  Registration  Statement on Form S-3
("Registration  Statement") to be filed by Barrett  Business  Services,  Inc., a
Maryland  corporation  ("Company"),  with the Securities and Exchange Commission
for the purpose of  registering  under the  Securities  Act of 1933, as amended,
157,443 shares  ("Shares") of the common stock, $.01 par value per share, of the
Company to be  offered  and sold from time to time by the  selling  stockholders
("Selling  Stockholders")  referred to therein.  Ninety  thousand of such Shares
(the  "Warrant  Shares") are issuable on exercise of warrants held by certain of
the Selling Stockholders.

                  As counsel for the Company,  we are familiar  with the actions
taken by the  stockholders and board of directors of the Company with respect to
the  authorization  and issuance of the Shares.  We have  examined  originals or
copies, certified or otherwise identified to our satisfaction, of such corporate
records, certificates of public officials, and other documents as we have deemed
necessary or relevant as a basis for the opinion set forth herein.

                  Based on the foregoing, it is our opinion that (a) the Warrant
Shares  have  been duly  authorized  and when (i) said  warrants  have been duly
exercised and (ii) the Warrant Shares have been duly delivered  against  payment
therefor  pursuant to the terms of said  warrants,  the  Warrant  Shares will be
validly issued, fully paid and nonassessable;  and (b) the balance of the Shares
are validly issued, fully paid and nonassessable.


                                                                       EXHIBIT 5






Barrett Business
 Services, Inc.                      - 2 -                         April 2, 1997


                  We  consent  to the use of this  opinion  in the  Registration
Statement and in any amendments thereto.

                              Very truly yours,

                              /s/ Miller, Nash, Wiener, Hager & Carlsen LLP

                              MILLER, NASH, WIENER, HAGER & CARLSEN LLP