Born in Whitewater, Wisconsin, he was raised in Plymouth, Michigan. He wanted to be a singer as a small child, but switched to acting when his voice changed. Within a month of moving to New York City, he became the understudy for Peter Firth in the Broadway production of Equus. He was nominated for a Tony Award for A Few Good Men.

His first film role was in the James Dean-influenced film 9/30/55 in 1977. His next was in the highly popular National Lampoon's Animal House. In 1984 he was nominated for the Academy Award for Best Actor for his performance of Mozart in Amadeus, losing out to his co-star, F. Murray Abraham. Other films include Dominick and Eugene, Shadow Man, Parenthood, Those Lips, Those Eyes, Echo Park, Mary Shelley's Frankenstein, and Slam Dance. He also played 1960s Civil Rights activist Michael Schwerner in the 1990 TV-movie Murder in Mississippi.