Additional screen credits include Separate Tables, Four Horsemen of the Apocalypse, The Courtship of Eddie's Father, The Hallelujah Trail, No Way to Treat a Lady, Soldier Blue, Sometimes a Great Notion, and A Matter of Time.
For television, Gay has adapted numerous literary classics, including The Red Badge of Courage, Captains Courageous, Les Misérables, A Tale of Two Cities, The Hunchback of Notre Dame, Ivanhoe, Uncle Tom's Cabin, and Around the World in 80 Days.
He also wrote television biopics of Howard Hughes, George Armstrong Custer, Caryl Chessman, and Adolf Hitler; small screen remakes of Dial M for Murder, Witness for the Prosecution, Inherit the Wind, and Shadow of a Doubt; adaptations of the bestsellers Fatal Vision and Blind Faith by Joe McGinniss and The Burden of Proof by Scott Turow; and the television movie A Piano for Mrs. Cimino starring Bette Davis.
Gay also wrote the one-man play Diversions and Delights, in which Oscar Wilde presents a lecture about his career to a Parisian audience in November 1899.
With Vincent Price portraying Wilde, the play premiered in San Francisco in July 1977 and toured more than 300 cities during the next three years.