John Tudor pitched a three-hitter and Willie McGee had four hits and stole two bases last night in Montreal as the St. Louis Cardinals defeated the Expos, 4-0.

Tudor (8-7) went the distance for the fourth time this season, striking out six. He didn't walk a batter and didn't allow a runner past first base.

"It helped that I was able to get ahead of hitters," said Tudor, voted the league's pitcher of the month for June. "I was moving the ball around and changing speeds, and I had command of all my pitches."

The Cardinals, in boosting their National League East lead to 1 1/2 games over the Expos, took a 3-0 lead in the first inning with four hits off David Palmer (6-7).

Vince Coleman led off with a single and, after a half-dozen pickoff attempts by Palmer, stole his major league-leading 54th base. Palmer's pickoff attempt at second went into center field, advancing Coleman to third. He scored on McGee's infield single.

Tom Herr followed with a walk and went to second when McGee was thrown out leading a double steal. Jack Clark doubled him home, then scored on Terry Pendleton's base hit.