Keszler received his BS at Southwestern Oklahoma State University in 1979. He worked on his PhD in Northwestern University under the supervision of Prof. James A. Ibers and received his degree in 1984. He continued his career as a postdoctoral fellow at Cornell University under the supervision of Prof. Roald Hoffmann in 1984–1985.
Keszler joined the faculty of Oregon State University in 1985 as an assistant professor. He became an associate professor in 1990, professor in 1995 and distinguished professor in 2006.