Stadler won his first two PGA Tour events in 1980, at the Bob Hope Desert Classic and the Greater Greensboro Open. His career year was 1982 when he won four PGA Tour events including the Masters Tournament after a playoff with Dan Pohl and the World Series of Golf at the end of the year. His next win was at the 1984 Byron Nelson Classic. Despite playing relatively well, Stadler did not win a PGA Tour event for over 7 years (May 1984 – November 1991) during the heart of his career. During this period he recorded six runner-up performances and dozens of top-10s on the PGA Tour. He had more success at winning international tournaments. He won the 1985 Swiss Open on the European Tour and the 1987 Dunlop Phoenix Tournament on the Japan Golf Tour. He had great success at the Scandinavian Enterprise Open too, an official event on the European Tour, finishing runner-up at the 1983 and 1986 events until finally winning in 1990. His winless steak in America was broken at the final event of the 1991 season, defeating Russ Cochran in a playoff at the Tour Championship.
Stadler won the B.C. Open in 2003, becoming the first player over age 50 to win a PGA Tour event in 28 years and the first player ever to win on the PGA Tour after he had won on the Champions Tour. He won 13 PGA Tour events in all, and played on the 1983 and 1985 Ryder Cup teams.