In 1973, Fosse was traded along with Jack Heidemann to the Oakland Athletics for Dave Duncan and George Hendrick. He played in 143 games that season, the most of his career, on a team with three 20-game-winning pitchers: Ken Holtzman, Vida Blue, and Catfish Hunter. Fosse guided the Athletics pitching staff to the second best team earned run average as well the second most shutouts in the American League as, the Athletics won the AL Western Division pennant by six games over the Kansas City Royals. The Athletics then defeated the Baltimore Orioles in the AL Championship Series. Fosse made his mark in the series, throwing out five would-be base stealers. The Athletics went on to win the World Series against the New York Mets.