(written from a Production point of view)
He is best known for his Emmy-nominated role as Detective Ron Harris in the television series Barney Miller, from 1975 through 1982. TOS guest actor James Gregory (Tristan Adams) and DS9 guest star Gregory Sierra (Entek) were also regulars on this series, and George Murdock was a recurring player.
He has more recently acquired some fame playing Shepherd Book in the cult science fiction series, Firefly. Glass reprised his role in the 2005 feature film adaptation of the show, Serenity. The film also featured fellow Star Trek actors Marley S. McClean, Amy Wieczorek, and Terrell Tilford.
Other credits of his include the made-for-TV movies Shirts/Skins (1973, starring Rene Auberjonois), The Crazy World of Julius Vrooder (1974, with Lawrence Pressman and William Lucking), Crash (1978, starring William Shatner and Adrienne Barbeau), Perry Mason: The Case of the Shooting Star (1986, with David Ogden Stiers), and Incognito (1999, with Phil Morris, Vanessa Williams, and Patti Yasutake). He also co-starred with Charles Napier and Julie Newmar in the 1987 science fiction film Deep Space, and with Bruce Davison, Dennis Christopher, and Sally Kellerman in the 1996 drama It's My Party.
Glass voiced the character of Randy Carmichael on the hit animated series Rugrats, from 1994 through 2004. He voiced the character on the spin-off series, All Grown Up. TNG and DS9 guest star Michael Bell also lends his voice to the series.