After smaller roles, such as Private Williams in Reflections in a Golden Eye, he starred in the critically acclaimed 1969 film Medium Cool. After starring roles in the TV shows Banyon (1972) and Nakia (1974), he played mostly supporting roles in action and horror films including Disney's The Black Hole (1979). Forster had lead roles in cult B-movies in the 1980s like Alligator (1980), Vigilante (1983), The Delta Force (1986), and The Banker (1989). He was nominated for an Academy Award for Best Supporting Actor in 1997 for Jackie Brown, which he credits with reviving his career. A busy actor, he has since gone on to appear in Like Mike; Mulholland Drive; Me, Myself, & Irene; Lucky Number Slevin and Firewall, to name a few. He recently appeared in the made for television movie The Hunt for the BTK Killer, as the detective intent on capturing serial killer Dennis Rader. Forster also played the father of Van on the short-lived Fox series Fastlane.