Foster was born in Evanston, Illinois, where he graduated from Evanston Township High School, and attended Kishwaukee College. He was selected by the Montreal Expos in the 29th round of the 1987 Major League Baseball draft, and debuted with two September 1993 games as a late-season call-up for the Phillies. The following spring, he was traded to the Cubs, where appeared in 89 of his 100 MLB games, with 82 starts, and posted all 32 of his career wins. In one of his starts, Foster picked up the Cubs’ first victory against the Chicago White Sox in interleague play, an 8–3 triumph at Comiskey Park on June 16, 1997. Exactly one year later, Foster worked in his last game as a Cub before returning to the minor leagues. His last MLB trial came during July and August 2001 as a relief pitcher for the Texas Rangers.