Stewart studied opera in New York City and eventually became an understudy to Robert Goulet in the Broadway production of Camelot. After being cast as Mike Bauer on Guiding Light, Stewart continued to perform in musical theater and nightclubs. Prior to Guiding Light, he appeared on numerous episodes of the 1960s television series Dragnet.
After leaving Guiding Light, Stewart relocated to California, where he made guest appearances in a number of television series, including L.A. Law, Highway to Heaven, and Knots Landing. He also provided the voice of Clem in the 1991 film Rover Dangerfield. His final role was in a 2001 episode of JAG.