An Illinois native, Irwin was a founding member of the acclaimed Chicago-based Steppenwolf Theater Company, with whom he started working directly out of college. Irwin played important roles in some of Steppenwolf's most celebrated productions. He made his Broadway debut in their Tony Award-winning production of "The Grapes of Wrath" (1990), originating the role of the narrator/ragman. Irwin appeared on the big screen as an earnest doctor supporting Lena Olin and Richard Gere in "Mr. Jones" (1993), and as Goldie Hawn's well-meaning colleague in the psychological thriller "Deceived" (1991).