Bartlett Sher will stage Theresa Rebeck's The Butterfly Collection and Mark Brokaw will direct Kenneth Lonergan's new, yet-untitled play in the Playwrights Horizons' 2000-2001 mainstage season.

A more complete picture of the nonprofit's upcoming season is emerging, with dates and fresh plot teases. Titles and playwright were previously reported.

Per the season brochure, the slate includes:

• The Butterfly Collection, by Rebeck, directed by Sher, begins previews Sept. 8, opens Oct. 1 and continues to Oct. 15. "When a spirited young writer's assistant invades a New England family, long-seeded tensions are dragged out into the open. Over the course of three tumultuous weeks, fathers, sons, lovers and spouses are pitted against one another in a ferocious battle of wits of wills that may claim them -- or restore a tenuous happiness."

• The Wax, by Tolan, begins previews Nov. 24, opens Dec. 17 and continues to Dec. 31. Director to be announced. "Who knows what will happen at an out-of-town wedding? In a hotel by the sea, a bevy of soul searching writers and scientists find themselves in full midlife existential crisis, and in a bedroom farce, to boot. Lust and love, passion and poetry collide in this hilarious roll on the middle aged hay." • A New Play, Lonergan, directed by Brokaw, begins previews Feb. 16, 2001, opens March 11 and continues to March 25. "In the lobby of an urban apartment complex, in the aftermath of a brutal murder, four disparate souls -- two young cops, a restless security guard and his tightly wound supervisor -- are forced to confront the truth about themselves, their relationships and the city they call home."

• A Play or Musical to be announced, begins previews May 4, 2001, opens May 27 and continues to June 10.

The 141-seat Off-Broadway nonprofit, committed to shepherding playwrights and new works, will also offers plays in its smaller studio space. Tim Sanford is artistic director of Playwrights Horizons.

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Lonergan has been lauded for his spare, unsentimental storytelling with This is Our Youth and The Waverly Gallery.

Rebeck won a Peabody Award for her teleplays for "NYPD Blue." Her plays include Sunday on the Rocks, Spike Heels, A View of the Dome, Loose Knit and Abstract Expression.

Tolan's A Girl's Life, a coming-of-age drama, has been seen regionally and was a finalist in 1997's Susan Smith Blackburn Prize competition. She was a member of Andre Gregory's Manhattan Project in the early 1970s. Her work has been produced at Playwrights Horizons, the Public Theater, Actors Theatre of Louisville and elsewhere.

For information about Playwrights Horizons, check out the web site at www.playwrightshorizons.org, or call (212) 279-4200.

-- By Kenneth Jones