(written from a Production point of view)
Outside of Star Trek, he is probably best known for his recurring role as Warden Martin Querns on the HBO television series Oz. He had previously worked on the PBS series Square One TV with Larry Cedar.
Cathey appeared in an episode of Spenser: For Hire, starring Avery Brooks. In 2002, Cathey appeared in an episode of Law & Order: Criminal Intent with fellow TNG guest star Olivia d'Abo, and in 2005, he co-starred with Gerrit Graham in an episode of Third Watch.
In 1995, he appeared in the made-for-TV movie Tyson, along with Paul Winfield, James B. Sikking, George Murdock. Five years later, he appeared in Homicide: The Movie, co-starring Ed Begley, Jr. and Michelle Forbes.
Cathey has a number of feature film to his credit. Two of his more prominent film roles were in movies based on comic books: 1994's The Mask, which featured Christopher Darga and Robert O'Reilly, and 1995's Tank Girl, co-starring fellow Star Trek alumni Lori Petty, Malcolm McDowell, Jeff Kober, Ann Cusack, and Iggy Pop. He also appeared in such high-profile thrillers as Se7en (1997) and American Psycho (2000).
Among his other films are Born on the Fourth of July (1989, also featuring Ed Lauter, Richard Poe, Bob Gunton, Mark Moses, and Mike Starr), Loose Cannons (1990, with Ronny Cox, Leon Rippy, Thomas Kopache, and Brad Greenquist), Clean Slate (1994, with Olivia d'Abo, Brad Blaisdell, and Ian Abercrombie), Clear and Present Danger (1994, with Harris Yulin, Raymond Cruz, Vaughn Armstrong, and Elizabeth Dennehy), and S.W.A.T. (2003, with Bruce Gray).