Singleton was acquired along with Mike Torrez by the Orioles from the Expos for Dave McNally, Rich Coggins and minor-league right-handed pitcher Bill Kirkpatrick at the Winter Meetings on December 4, 1974. During his ten years in Baltimore, Singleton played the best baseball of his career as the Orioles won two pennants, in 1979 and 1983, and won the 1983 World Series. In 1977, he posted a career-high .328 batting average, third highest in the American League. In 1979 he had career-highs with 35 home runs and 111 RBIs. He was described by his manager with the Orioles Earl Weaver as "the kind of hitter who can start a rally by getting on base or end one by driving in the winning run." Being a slow runner was the only deficiency he had as a ballplayer. Singleton played in his final major league game on September 25, 1984, at the age of 37.