The Merriweather Post Pavilion -- which along with Wolf Trap is one of the area's major summer concert venues -- unveiled part of its 1986 schedule this week. Wolf Trap will announce its full schedule Wednesday.

The Post Pavilion season will kick off with Willie Nelson on May 26, Memorial Day, and will run into mid-September. Charles Blum, director of advertising and promotion for the Post Pavilion, expects to book at least as many concerts as last year, when there were 54, attracting almost half a million fans. "A lot of acts are going to be out there touring this summer," Blum said, "but their schedules are not yet finalized." The series will once again be sponsored by the Miller Brewing Co.

Highlights include a new jazz subscription series, Barbara Mandrell's first local appearance since suffering serious injuries in a car accident in September 1984, and concerts by Julian Lennon, Culture Club, the Moody Blues and the Pointer Sisters. The Beach Boys, who have made their summer stops on the Mall in recent years, will celebrate their 25th anniversary Aug. 17 at the pavilion. Earlier this week, a Park Service spokesman said the band still owed $98,200 for expenses during last summer's free Mall concert and that the bill had been turned over to a private collection agency. With interest, the bill now comes to $126,580.37.

Initially, Post Pavilion tickets will be available only by mail-order series subscriptions (ads will be running this Sunday in The Washington Post and the Baltimore Sun). There are eight series available:

*Jimmy Buffett (July 2), the Moody Blues (July 22), comedian Billy Crystal (Aug. 8), the Beach Boys (Aug. 17) and another act to be announced (probably Jackson Browne).

*Steve Lawrence and Eydie Gorme (Aug. 5), Joan Rivers (Aug. 24), Mandrell (Sept. 13) and French pop singer Charles Aznavour (date TBA).

*Robert Palmer (date TBA), Stevie Ray Vaughan and Double Trouble, and the Fabulous Thunderbirds (June 27), .38 Special (July 15), Loverboy (Aug. 10) and an act to be announced.

*Lennon (June 7), Starship (July 9), Mr. Mister (July 25), Culture Club (Aug. 31) and an act to be announced.

*Depeche Mode (June 14), the Cure (July 11), Joe Jackson (TBA), Eurythmics (Sept. 3) and an act to be announced.

*Nelson (May 26), the Oak Ridge Boys (Aug. 31), the Judds (date TBA) and an act to be announced.

*Billy Ocean (June 28), the Four Tops and the Temptations (July 5), the Pointer Sisters (Aug. 7), Kool & the Gang (Aug. 9) and an act to be announced.

*Chick Corea, Al Di Meola and Wayne Shorter (June 26), Jean-Luc Ponty (Aug. 3), Andreas Vollenweider (Aug. 14) and Manhattan Transfer (Aug. 15).