He was active in American movies and TV shows, such as his memorable supporting role as the trial judge in the Sidney Lumet's "The Verdict" with Paul Newman, an episode of "The Golden Girls" in 1987, and portraying Chief Justice of the United States Roy Ashland in the TV series "The West Wing". In 1992, O'Shea guest starred in the Season 10 finale of the sitcom "Cheers", and, in 1995, in an episode of the show's spin-off "Frasier". He appeared in the pilot episode of "Early Edition" as Sherman.