For his portrayal of bail bondsman Max Cherry in Quentin Tarantino's Jackie Brown (1997), he was nominated for Academy Award for Best Supporting Actor.

Forster played a variety of both leading and supporting roles in over 100 films, including Captain Dan Holland in The Black Hole (1979), Detective David Madison in Alligator (1980), Abdul Rafai in The Delta Force (1986), Colonel Partington in Me, Myself & Irene (2000), Scott Thorson in The Descendants (2011), General Edward Clegg in Olympus Has Fallen (2013) and its sequel London Has Fallen (2016), Norbert Everhardt in What They Had (2018), and Sheriff Hadley in The Wolf of Snow Hollow (2020).

[9] Forster also appeared in episodes of the TV series N.Y.P.D., Judd for the Defense and Premiere, the latter also featuring Dustin Hoffman and Sally Kellerman.

Forster was then cast in another key role in an important movie: part-Indian Army scout Nick Tana in Robert Mulligan's The Stalking Moon (1968); he was billed third, after Gregory Peck and Eva Marie Saint.

Forster had a key support role in Justine (1969), directed by George Cukor and starring Dirk Bogarde, which was a huge flop.

[10] Forster played a tormented priest in Pieces of Dreams (1970) and a student filmmaker in Cover Me Babe (1970), which was a box office flop.

"[9] In 1973, he briefly returned to Broadway playing Stanley Kowalski in a revival of A Streetcar Named Desire, opposite Julie Harris.

[16] Forster moved into lower-budgeted movies, starring in Stunts (1977) for Mark L. Lester[17] and Avalanche (1978), the latter opposite Rock Hudson and Mia Farrow for Roger Corman's New World Pictures.

"[18] Forster appeared in the thrillers Satan's Princess (1989) and The Banker (1989), the mini series Goliath Awaits (1981), and episodes of Magnum, P.I., Tales from the Darkside, Hotel, Crossbow, and Jesse Hawkes.

Forster's films by this stage were almost entirely low budget ones: Peacemaker (1990), Checkered Flag (1990), Countdown to Esmeralda Bay (1990), Long Way Back (1990), Committed (1991), Diplomatic Immunity (1991), 29th Street (1991), In Between (1992), In the Shadow of a Killer (1992), Maniac Cop 3: Badge of Silence (1993), South Beach (1993), American Yakuza (1993), Cover Story (1993), Point of Seduction: Body Chemistry III (1993), Scanner Cop II (1995), Guns & Lipstick (1995), The Method (1995), Original Gangstas (1996) (directed by Larry Cohen), Uncle Sam (1996), Hindsight (1996) and American Perfekt (1997).

Forster appeared in Jackie Brown as bail bondsman Max Cherry, which earned him a nomination for the Academy Award for Best Supporting Actor in 1997.

[19] He subsequently had consistent work in the film industry, appearing in Like Mike, Mulholland Drive, Supernova, Me, Myself & Irene (2000), Human Natyre (2001), Confidence (2003), Charlie's Angels: Full Throttle (2003), Lucky Number Slevin (2006), and Firewall (2006).

He appeared in the hit NBC series Heroes as Arthur Petrelli, the father of Nathan and Peter Petrelli, as well as the Emmy Award-winning AMC crime drama Breaking Bad as Walter White's new-identity specialist Ed Galbraith (a role he reprised in El Camino: A Breaking Bad Movie and Better Call Saul).

[20] He was the first choice to play Sheriff Harry S. Truman in David Lynch's Twin Peaks, but had to turn it down due to a prior commitment to a different television pilot, and was replaced by Michael Ontkean.

He appeared in Lynch's Mulholland Drive, a pilot for a TV series that was not picked up but was later turned into a critically acclaimed movie, and finally appeared in Twin Peaks, playing the brother of Sheriff Harry S. Truman, Sheriff Frank Truman, in Twin Peaks: The Return, when Ontkean was not available to reprise his role.

[25] In June 2019, Forster was diagnosed with a brain tumor, and he died from the disease at his home in Los Angeles on October 11, 2019, at the age of 78, on the day El Camino: A Breaking Bad Movie was released.