Overall pitched even better in 1907. He went 23–7 with eight shutouts and a 1.68 ERA. He also won a game in the 1907 World Series, and the Cubs won their first title. In 1908, Overall "slumped" to just 15 wins but also won twice in the 1908 World Series as Chicago repeated as champions. In that Series, Overall set a Cubs record for most strikeouts in a World Series game by a single pitcher (10), which still stands. In the series-clinching game, he shut out the Detroit Tigers on three hits. In the first inning of that game, he became the only pitcher to strike out four hitters in one inning in a World Series game, and the last to do it in a playoff game until 2013 when is was duplicated by Aníbal Sánchez of the Tigers. In 1909, he won 20 games and set a career-low in ERA (1.42). He also led the NL in strikeouts, with 205.