The Baltimore Orioles, out of contention in the American League East fairly early this season, are expecting a decrease in attendance of 150,000 persons from last year, their second highest home gate ever.

In 1977, the Birds, contenders in the divisional race throughout the season, drew 1,195,769 persons through Memorial Stadium turnstiles and sustained a net operating loss of $43,846.

Oriole General Manager Hank Peters figures the club will lose upward of $350,000 this season in ticket and concession revenue alone, even before the players' salaries and bonuses - are added.

Now languishing in fourth place in the AL East and trailing the Boston Rex Sox by seven games - although the O's record is better than 20 other major-league teams - the Orioles are behind last year's 64-date mark of 993,740 by 31,497.

Alan Harazin, director of business affairs for the Orioles, said he thought a "fair guesstimate" of the Bird's final attendance this year might be 1,050,000. He attributed the projected decrease to the club's standing this year - last season they were two games out at this time - and four rainouts. There were no rainouts last year.

Additionally, Harazin said, the 52,860-seat stadium was sold out last year for special festivities honoring retiring Oriole Brooks Robinson. There have been no sellouts this year. The highest attendance was for the Red Sox (38,542) on July 1; the lowest for the Toronto Blues Jays (4,452) on May 18.

The Red Sox and the New York Yankees - traditionally big draws in Baltimore - did little to boost the sagging gate in the past week. The average attendance for a two-game series with the Yanks last month was 30,000.Last week, the two-game average was 18,000.

When the Red Sox last visited Baltimore in late June-early July, the average attendance was 33,000-plus for three games. This past week, the three-game series draw an average 14,000.

(AL expansion in 1977 has resulted in fewer games against crowd-pleasing Boston and New York - another factor in the dropping attendance.)

Bad weather has contributed to the attendance decline. With the rainouts and delayed games, fans have been more cautious about checking the forecast before setting off for the park. Advance sales have been hurt.

"I think we've had a hurricane hanging off the coast all season," said Peters. "In some cases, it's literally put a damper on people coming out and dampened enthusiasm."

While not happy about this year's attendance, Peters said. "If we can draw as much as 1,062,000 people, that would be our best year since 1966 (1,203,366), the record, other than last year."

The Orioles managed an after-tax profit of $580,788 last year because of a one-time expansion income of $931,250. An increase of $499,000 in the player payroll was the primary reason for the club's net operating loss of $43,846.

Without expansion income this year, and with attendance lower than last year, Peters anticipates a deficit. "It's difficult to determine what it will be until we get down to the end of October . . .

"There are things we don't know now. Certain players have the ability to become free agents . . . sometimes signing them requires bonuses . . . "

Peters said the types of offers the Orioles are making are commensurate with those of other clubs.

"Maybe some of the things that have happened in the past - like some clubs going insane with offers - won't happen again," he said. "We'll continue to negotiate with players. We have made some very fine offers. In some cases, they're equal to what other clubs have made, but certain other factors have caused the players to go elsewhere."