After serving in the United States Air Force, he went to New York University and earned a master's degree in drama.
He appeared in such television programs as CHiPs; Custer; Nakia; Matlock; Matt Houston; Mike Hammer; Magnum, P.I.
In 1969, DeBenning appeared as Orrey Hills on the TV series The Virginian in the episode titled "Journey to Scathelock".
His film appearances included a memorable turn as a comic prone Marine in Beach Red (1967), Sweet November (1968), St. Ives (1976), The Incredible Melting Man (1977), Armed Response (1986), A Nightmare on Elm Street 5: The Dream Child (1989), and Love Field (1992).
He played Lt. Jim Porter, a Navy Intelligence agent, in the 1978 science fiction TV miniseries, The Return of Captain Nemo,[2]: 888 originally shown on U.S. TV as a three part miniseries (50-minutes each episode) and later released theatrically outside the U.S. in a 102-minute widescreen version renamed The Amazing Captain Nemo.