For the second year in a row in 1970, the Orioles faced the Twins in the ALCS. Starting Game 2 for the Orioles, McNally held the Twins hitless for the first three innings as the Orioles scored three runs. In the fourth inning, McNally made the score 4–0 with an RBI single against Tom Hall. After walking Leo Cárdenas to lead off the bottom of the inning, he allowed back-to-back home runs to Killebrew and Oliva to make it 4–3. McNally never let the Twins score again, and the Orioles cruised to an 11–3 victory before ultimately sweeping the ALCS. This year in the World Series, the Orioles faced the Cincinnati Reds. Starting Game 3 of the series, McNally gave up a run in the second inning but held the Reds to just that through the first six innings of the game; meanwhile, Baltimore gave him for runs of support. After Tony Cloninger of the Reds walked Paul Blair with one out in the sixth, Cloninger was replaced with Wayne Granger, who allowed a double to Brooks Robinson and intentionally walked Davey Johnson before striking out Andy Etchebarren, bringing McNally to the plate with the bases loaded and two outs. McNally helped his own cause, depositing a pitch from Granger in the left field seats and becoming the only pitcher in major league history to hit a grand slam in a World Series. He went on to allow two more runs, but the Orioles led by more than enough in their 9–3 victory. After losing Game 4, the Orioles defeated the Reds in Game 5, making McNally a World Series champion for the second time in his career. The bat McNally hit the grand slam with (lent to him by Motton) is at the Baseball Hall of Fame in Cooperstown.