From 1980 on, Steinkamp co-edited most of Pollack's films with his father; after his father's retirement in 1995, William Steinkamp became Pollack's principal editor through the end of the latter's career in 2005.
Steinkamp has edited several of director Gary Fleder's films, from Kiss the Girls (1997) through The Express (2008).
He was again nominated as sole editor for The Fabulous Baker Boys (directed by Steve Kloves, 1989).
He has been nominated for ACE Eddie awards for editing Tootsie (1982), Out of Africa (1985), and Scent of a Woman (directed by Martin Brest - 1992).
Steinkamp has been selected for membership in the American Cinema Editors.