The Milwaukee Brewers and Montreal Expos clinched their first-ever baseball playoff berths with victories yesterday, and the Houston Astros advanced as they waited to play a game on the West Coast.

Those three teams join Kansas City, which earlier clinched the American League West's second-half championship, in the major leagues' playoff setup resulting from the settlement of the midseason players' strike. None of the first-half divisional winners -- the New York Yankees, Oakland A's, Philadelphia Phillies or Los Angeles Dodgers -- won second-half titles.

The regular season ends today.

Milwaukee clinched the AL East title with a 2-1 victory over Detroit in Milwaukee. The Brewers open the divisional series at home against the Yankees Wednesday night.

Montreal captured the NL East with a 5-4 victory over the New York Mets in New York. The Expos will open the playoffs at home against the Phillies Wednesday afternoon.

Houston advanced when Atlanta defeated Cincinnati, 4-3, in Cincinnati, thus leaving the team with the major leagues' best record (65-42) on the sidelines. Houston later lost at Los Angeles, 7-2, but was playing reserves by the third inning against its playoff opponent. The Astros-dodgers series begins in Hopuston Tuesday night.

The AL West series between the Royals and Oakland A's begins Tuesday afternoon in Kansas City.

In yesterday's game at Milwaukee, Gorman Thomas drove in the go-ahead run with a bases-loaded sacrifice fly in a two-run Milwaukee eighth inning.

Rollie Fingers (6-3), the major league's leader in saves with 28, earned the victory with 1 1/3 innings of shutout relief.

Losing pitcher Jack Morris (14-7) carried a six-hitter and a 1-0 lead into the eighth. But Paul Molitor drew a leadoff walk. Robin Yount then pushed a bunt toward first base and Ron Jackson, the first baseman, hesitated after fielding the ball and his throw was late to first as both runners were safe.

Cecil Cooper, whose sixth-inning error allowed the Tigers' run to score, then bunted down the third base line. Morris picked up the ball but had no play as Cooper beat it out for a single to load the bases.

Ted Simmons followed with a hard liner that Morris deflected to shortstop Alan Trammell, who threw to first for the out as Molitor scored the tying run. An intentional walk to Ben Oglivie loaded the bases and Yount scored the winning run on Thomas' fly to right.

In New York, pinch-hitter Wally Johnson, in the major leagues for less than a month, hit a two-run triple in the seventh inning that boosted Montreal to its victory.

Neil Allen (7-6) was the victim of the rally, while Bill Lee, the Expos' third pitcher, picked up the victory and raised his record to 5-6.

At Cincinnati, Bob Horner hit two home runs, drove in three runs and scored the winning run on second baseman Ron Oester's eighth-inning throwing error as Atlanta eliminated the home team from playoff contention.