Pro-Football-Reference.com's Player Season Finder can produce a list of quarterbacks that have started at least one game for the Pittsburgh Steelers. Alternatively, the Steelers' team page on Pro-Football-Reference.com has a list of year-by-year starting lineups, including quarterbacks who started the most games in a given year.
The two quarterbacks who have started the most games for the Steelers are Terry Bradshaw and Ben Roethlisberger. Roethlisberger started 158 games for the Steelers between the 2004 and 2014 seasons; Roethlisberger is still active in 2015. Bradshaw started 158 games during his Steelers career from 1970 to 1983. Roethlisberger won two Super Bowls for the Steelers, while Bradshaw won four. Other notable quarterbacks who have started for the Steelers include Kordell Stewart, Neil O'Donnell, Bobby Layne, Jim Finks and Bubby Brister.