(written from a Production point of view)
Marshall attended the Juilliard School, where his mentor was John Houseman. Marshall's classmates included Kelsey Grammer, David Ogden Stiers, Kevin Kline and Robin Williams. Marshall first met Scott Bakula when performing in a production of Shenandoah. ("Marshall Decree", Dreamwatch issue 37)
Marshall made his first acting appearances in 1979, with appearances in the motion picture Tilt (with Don Stark) and a guest starring role in the How the West Was Won episode "The Forgotten", with Fionnula Flanagan and David Warner. In 1980, Marshall starred as Tony in a revival of West Side Story on Broadway.
Marshall later played the titular character in the 1982 series Marco Polo (with Leonard Nimoy, David Warner and F. Murray Abraham). He later starred in the films La Pelle, Claws and Krull, in which he played the main character Prince Colwyn. Marshall participated in the audio commentary for the DVD release of the film. His other motion picture credits include The Stay Awake, Feds (with Larry Cedar), The Gods Must Be Crazy II, Burndown, Berlin '39 (with John Savage) and Amberwaves.
Marshall was no stranger to science fiction prior to being cast in DS9. In 1991 he guest-starred in the Quantum Leap episode "A Hunting Will We Go", (with Jeffrey King). Star Trek: Enterprise star Scott Bakula played the lead in the series alongside guest actor Dean Stockwell. Marshall's other television guest star credits include In the Heat of the Night (directed by Paul Lynch), Baywatch (with Monte Markham and Kay E. Kuter), Hunter (with Jeffrey Combs, Ellen Wheeler and Gene Dynarski), The Commish (with Kaj-Erik Eriksen and Julian Christopher), Silk Stalkings (with Charlie Brill, Tim de Zarn and Cyndi Pass) and JAG.