After playing violin in high school for musicals, Marshall tried his luck on stage, and was cast as Curley in his senior year's production of Oklahoma!
After graduating, Marshall then spent four years in the drama department at The Juilliard School with the likes of Kelsey Grammer and Robin Williams.
While at Juilliard, he had his first professional experience with Joseph Papp's Shakespeare in the Park and spent the next 14 years in New York City doing theater, film and TV, including being cast as Tony in the first Broadway revival of West Side Story.
Although appearing in such films such as Tilt (1979), The Skin (1981), and Feds (1988), he is perhaps best known for the starring role as Prince/King Colwyn in the fantasy adventure movie, Krull (1983).
He lives with his wife, Linda, who also graduated in 1968 from Saint Joseph High School (SJHS).