Entering the 1971 season, the Orioles raised McNally's salary to $85,000. He held the Senators to two runs on Opening Day (April 7) in a complete-game, 3–2 victory. On April 23, he and Clyde Wright of the California Angels held each other's teams to two runs until the ninth, when the Orioles scored six times to give McNally an 8–2 victory. On September 7, he limited Cleveland to one run over nine innings and hit a two-run home run against McDowell in a 3–1 victory. A sore arm kept McNally from pitching for six weeks in July and August, but he was still the first Oriole to win 20 games when he threw a shutout against the Yankees on September 21. McNally was one of four 20-game winners for the 1971 Orioles (Pat Dobson, Palmer, and Mike Cuellar were the other three). They were the first quartet of pitchers to each win 20 games for the same team since four members of the 1920 Chicago White Sox each won 20. McNally led the Orioles with 21 wins, tying with Catfish Hunter for fourth in the AL; his 2.89 ERA ranked seventh; and he led the AL with a .808 winning percentage. In 30 starts, his record was 21–5, and he struck out 91 batters in innings. He finished 4th in AL Cy Young Award voting and 11th in AL MVP balloting. His streak of four 20-win seasons in a row was the first in the AL since Red Ruffing did so from 1936 through 1939.