Despite blacklisting because of his supposed communist connections, Marshall continued to appear in both television and films. He appeared on the British spy series "Danger Man" in episodes titled "Deadline" (1962) and "The Galloping Major" (1964). Marshall played the role of traveling opera singer Thomas Bowers on the 1964 "Bonanza" episode "Enter Thomas Bowers," and that same year he appeared, with actor Ivan Dixon, as the leader of a newly independent African nation and as a T.H.R.U.S.H. agent in the first-season episode of "The Man from U.N.C.L.E." entitled "The Vulcan Affair", also on the 1964 "Rawhide" episode "Incident at Seven Fingers" where he played a "Buffalo Soldier". In 1968 he appeared as Dr. Richard Daystrom in the "" episode "The Ultimate Computer". In 1969, he had a special guest appearance as the character Amalek in an episode of "The Wild Wild West" entitled "The Night of the Egyptian Queen". He reprised his Othello persona in 1979 on Steve Allen's "Meeting of the Minds".