Hal McRae, in one of the worst slumps of his career, reached base four times and doubled to key a five-run rally in the fifth inning in Kansas City last night, leading the Royals to a 6-5 victory over Baltimore.

Jim Palmer, in his season debut , sailed into the fifth with a two-hitter and a 5-0 lead before the Royals scored five runs on six singles and McRae's double. McRae, hitting .154, doubled home George Brett with the third run of the inning and chased Palmer. Sammy Stewart (1-1) then surrendered a two-run single to Jerry Martin.

Amos Otis' RBI-single in the sixth scored John Wathan to break the tie. Dave Frost, in his Kansas City debut, relieved Larry Gura with one out in the fifth and got the victory. Dan Quisenberry pitched the final three innings, earning his second save.

The Orioles got to Larry Gura for a run in the second on doubles by Eddie Murray and Gary Roenicke, then went up, 3-0, with solo home runs by Murray in the fourth and Roenicke in the fifth. Rich Dauer's two-run double in the fifth scored Rick Dempsey and Al Bumbry for a 5-0 lead.

Singles by U.L. Washington and Tom Poquette launched the fifth-inning rally against Palmer. One out later, Brett singled, then Willie Aikens singled to load the bases and Otis hit a sacrifice fly ahead of McRae's double.

Murray, who has been one of the American League's hottest hitters, finished with a home run, a double and a single.