EXHIBIT 5.1

           [LETTERHEAD OF GRAY, PLANT, MOOTY, MOOTY & BENNETT, P.A.]

                                                  LINDLEY S. BRANSON
                                                  612 343-2827

                               January 29, 1999

Online System Services, Inc.
1800 Glenarm Place
Suite 800
Denver, CO 80202

          RE:  Form S-3 Registration Statement

Ladies/Gentlemen:

          This opinion is furnished in connection with the registration,
pursuant to the Securities Act of 1933, as amended, of up to 840,000 shares of
common stock, no par value (the "Shares"), of Online System Services, Inc. (the
"Company" or "OSS") issuable upon (i) conversion of the Company's Series C
Preferred Stock (the "Series A Preferred Stock") and (ii) exercise of
outstanding transferable warrants of OSS which may sold from time to time by
various selling shareholders for their own account.

          We have acted as counsel to the Company in connection with the
preparation of the Form S-3 Registration Statement (the "Registration
Statement").  We have examined the Articles of Incorporation, as amended, the
Bylaws of the Company, such records of proceedings of the Company as we deemed
material and such other certificates, records and documents as we considered
necessary for the purposes of this opinion.

          Based on the foregoing, we are of the opinion that the Shares will be,
when issued, legally issued, fully paid and non-assessable securities of the
Company.  We understand that this opinion is to be issued in connection with the
Registration Statement.  We consent to a filing of a copy of this opinion with
the Registration Statement.

                                 Very truly yours,

                                 GRAY, PLANT, MOOTY,
                                  MOOTY & BENNETT, P.A.



                                 By  /s/ Lindley S. Branson
                                     -----------------------------------
                                         Lindley S. Branson