Hi Bob -- thank you for posting to History Hub!
The starting point to locate testimony before the House Committee on Un-American Activities (HUAC) is in the published indexes: the cumulative (1938-1954) and the supplemental (1955-1960) are both freely available online via Hathi Trust. Unfortunately, I don't see an Orie Fuller listed in either publication.
I also checked our listing of executive session HUAC transcripts, which are arranged alphabetically by witness name, and through the HUAC files on named individuals. Once again, I don't see anything on an Orie Fuller.
There's also a combined cumulative index (1951-19712) for the Senate Internal Security Subcommittee (SISS) of the Senate Committee on the Judiciary -- which is a related committee to HUAC.
Generally, the best resource for locating congressional hearing transcripts is ProQuest Congressional, in particular the Hearings Digital Collection module. ProQuest is a subscription database that may be available to you via a local academic or law library.
Hearings can often by found freely available online through sources like Hathi Trust, the Internal Archive and Google Books -- particularly if you know the title the hearing was published under.