Gass taught at The College of Wooster for four years (1950-54), Purdue University for fourteen (1955-69), and Washington University in St. Louis for thirty, where he was a professor of philosophy (1969–78) and the David May Distinguished University Professor in the Humanities (1979–99). During his teaching career Gass completed seventeen residencies at fourteen institutes of higher education. Since 2000, Gass has been the David May Distinguished University Professor Emeritus in the Humanities. In 2006 Washington University established a William H. Gass professorship in Arts & Sciences.

For photographs of Gass at Washington University, see IMAGES. For recordings of Gass lectures and readings at Washington University, see SPEAKING ENGAGEMENTS.