He sailed through the first three innings in 20 pitches, finished the game in 104 and turned in the Baltimore Orioles' first complete game in spring training in at least nine years.

What Scott McGregor did to the Atlanta Braves in a six-hit, 6-3 victory today is no less than he has done to American League teams in 78 complete games in the past nine seasons. But this was different because of the circumstances.

Almost all the questions about the 1986 Orioles center on pitching, particularly starting pitching, and with a rotation that has turned in a dazzling 2.77 ERA the last six games, what had been a bleak spring training now looks incredibly positive.

In the manager's office, Earl Weaver said: "This is the way it used to be." In the general manager's office, Hank Peters said: "Earl is stretching them out to build up their arm and to build up their confidence. I know they're building up my confidence."

The game was even better for Baltimore than the box score indicates because the Braves got only one legitimate run off McGregor, that on catcher Ted Simmons' home run in the seventh. They scored twice in the eighth, but with two outs and after right fielder Lee Lacy lost a ball in the sun.

"That cost him eight to 10 pitches," Weaver said. "Lacy catches that ball, and you're looking at a complete game in less than 100 pitches. That's really good."

A week ago, McGregor had stepped off a bullpen mound and said: "I might as well quit this game. I've just forgotten how to pitch."

In his best years, he has that feeling every six weeks or so, and when he does, he goes to the bullpen and throws and throws and throws. Finally, he'll say something like: "Yeah, that's what it's supposed to feel like."

He got that feeling back against the New York Mets last Tuesday night by pretending he was pitching in a room with a low ceiling.

" Coach Elrod Hendricks said it didn't look like I was getting any push with my legs," McGregor said. "So I just started thinking of doing something to make me stay low and compact and push off with my legs."

He allowed 10 hits and two runs in six innings against the Mets, then was even better today, retiring the first 10 Braves and allowing only three base runners the first six innings.

In the process, he was at his best, getting his curve ball over for strikes and using low changeups and curves to set up high fast balls.

"Once you get in a groove, you don't have to think about what you're doing," he said. "I'm just very confident right now, but we all are. We're back where we used to be, where if we get someone on base we don't panic. If everything's going badly, we just step off the mound and say: 'It's not that bad.' I remember once last year Earl was screaming early in a game, and I asked: 'Why are you screaming?' He said: 'I'm waiting for something to go wrong.' We all were. Now, we're waiting for something to go right."

Each Orioles starter has gone at least seven innings in his most recent start, except Storm Davis, who has a pulled stomach muscle and lasted only four Saturday. The pitching has been so good that Weaver is sending his relievers to the minor league camp to get work and bringing in minor league pitchers for mop-up work.

"We used to do this all the time when George Bamberger was our pitching coach," Weaver said. "The only way to build up an arm is to let them pitch after fatigue sets in. You take your lumps down here, but you establish something for the regular season."

Pitchers Bill Swaggerty and Odell Jones and catcher Al Pardo were sent down today, bringing the roster to 29 players. Five more players will be cut by opening day. Pardo, 23, who hit only .133 (10 for 75) last year with the Orioles, impressed almost everyone this spring. He finished with a .316 batting average, two homers and six RBI. An umpire's mistake turned a third homer into a double. "He made a very good impression," Weaver said. "I said before that he'll catch in the major leagues." . . . Reliever Tippy Martinez (pulled muscle above left knee) didn't work again today, but is expected to run and throw Monday . . . Third baseman Floyd Rayford (bone chips in left thumb) won't work for a few more days, and there's concern he might not be ready for opening day . . . Davis (pulled stomach muscle) said he felt better, but was unable to throw.