When the Baltimore Orioles scored seven runs in the first inning tonight, there was every reason to think the game would be a laugher. It was, but nobody could have foreseen the extent to which the Orioles supplied the comedy.

The Orioles tied a club record by committing six errors, all by infielders as each position contributed, and they amassed that figure by the fifth inning. Still, they managed to win, 10-7, and complete a three-game sweep of the defending American League champion Milwaukee Brewers.

"Nobody said it had to be beautiful; they just said you had to win," said Baltimore Manager Joe Altobelli. Then, asked if his club might have become complacent with the big lead, he said, "I don't think you get that complacent."

After shortstop Cal Ripken Jr. had dropped a throw for the Orioles' third error of the fifth inning and Milwaukee had cut the lead to 9-6, a fan in left field made a fine catch of a foul drive.

"Give that fan a contract," intoned public address announcer Rex Barney, as he has done in routine fashion in recent years. But this time the reaction bordered on uproar, as critics among the 23,399 apparently suggested that the honoree be rushed right into action.

When the fifth inning ended, two female mud wrestlers were introduced, and they proceeded to wrestle with the team's mascot in left field. Obviously, this was not one of the high points of the baseball season.

The first-inning rally was the Orioles' biggest of the year, however. Milwaukee started left-hander Jerry Augustine, who had suffered knee and arm injuries earlier this spring that limited his playing time. Tonight, in his seventh appearance, only his pride was hurt.

The first five batters reached base safely, as John Shelby and Dan Ford doubled, Ripken walked and Eddie Murray and Gary Roenicke singled. After Augustine struck out Benny Ayala, Rich Dauer singled for a 4-0 lead and Jim Slaton was summoned to the mound.

In 34 innings, Slaton had yielded only one home run, so Leo Hernandez promptly lined a 1-1 pitch over the 376-foot sign on the left field fence. It was Hernandez's sixth homer and gave the Orioles a bigger first inning than most of the Colts' first periods last fall.

Shelby, a switch-hitter, batted left-handed and singled for his second hit of the inning before Slaton finally calmed things.

The Orioles began having trouble in the second, when starter Mike Boddicker walked Ben Oglivie, a no-no with two out and a seven-run lead. Charlie Moore's grounder caromed off third baseman Hernandez's shin for the first error and Jim Gantner took advantage with a three-run homer to right.

A double by Roenicke and a two-run, opposite-field homer by Ken Singleton, batting left-handed as a pinch hitter for Ayala, made it 9-3 after two innings. That gave the Orioles nine home runs in this series.

Error No. 2, first baseman Murray's muff of a foul fly, caused no harm in the third. However, in the fourth, Hernandez and the Brewers came close to a repeat of the second-inning scenario.

This time, Oglivie singled before Hernandez let Moore's potential double-play grounder go between his legs. Gantner again sent a long drive to right, but this time it was only a sacrifice fly, as Ford ran it down.

Three more errors helped the Brewers close within 9-6 in the fifth. Second baseman Dauer started it by mishandling Rick Manning's routine grounder for his second error of the season. Then Murray let Boddicker's pickoff throw get away, Manning moving to second. Manning scored on Robin Yount's triple off the fence in center.

Cecil Cooper's hard grounder went off Murray's glove, Yount scoring as the fans showed their displeasure. The boos became louder when Cooper was given a double, extending his batting streak to 12 games.

Murray grabbed Ted Simmons' liner and threw to second for an apparent double play, but Ripken dropped the ball. This time the boos turned to cheers when the error sign was posted.

Although Altobelli might have preferred to send in a new infield, he was forced to replace Boddicker as the sixth inning began because of a blister on the pitcher's middle finger.

Sammy Stewart and Tippy Martinez limited Milwaukee to one run and two hits over the last four innings, as the Orioles played errorless ball and the crowd offered sarcastic cheers for routine outs.

The final Baltimore run in the seventh was batted across by Hernandez, giving him four RBI to offset the four unearned runs for which he was responsible.

Ripken was philosophical about the Orioles' defensive troubles. "If you can still win making six errors, you're going okay," he said.