THE OPENING of Horizons Theater's "Scheherazade," scheduled for this Sunday, has been set back a week. Carole Myers, the female lead in the play, was returning home from rehearsal last week when she was injured in a head-on collision. Myers was badly bruised and shaken up, but received no major injuries.

Horizons artistic director Leslie Jacobson says Myers wanted to go ahead with the scheduled opening of Marisha Chamberlain's play, which is about a rape victim who distracts her tormentor with a variety of ploys until the police arrive. But Myers' role is a physically and emotionally taxing one, and the theater company decided to postpone for a week to ensure her recovery. The first preview of "Scheherazade" is Thursday; opening night is January 7.

Horizons has been invited to participate in the First International Women Playwrights Conference, to be held in October at the State University of New York at Buffalo. Among the 1,500 participants will be playwrights Alice Childress, Megan Terry (United States), Michelene Wandor (United Kingdom), Bai Fengxi (China) and Fatima Dike (South Africa). Anna Kay France, organizer of the multicultural conference, says that though nearly a third of the members of the Dramatists Guild are women, plays by women account for only about seven percent of the professional theater season. Last year, Horizons presented a stimulating symposium on women dramatists and "the female aesthetic," chaired by playwright Kathleen Betsko, one of the organizers of this year's conference.

For information on the conference, write France at the Department of English, 306 Clemens Hall, SUNY at Buffalo, Buffalo, NY 14260.

Shooting for the stars: The Shakespeare Theater at the Folger has replaced its planned season-closing production of the seldom-seen, politically potent "Coriolanus" with the more familiar "The Merchant of Venice." The Shakespeare Theater had been angling for name actors like Stacy Keach for the title role (William Hurt and Kevin Kline had been mentioned for its upcoming "Macbeth"). But when stars proved unavailable, director Michael Langham decided the theater was too small to encompass his vision of "Coriolanus" anyway. So Langham has cast Kelly McGillis, who played Tom Cruise's lover in "Top Gun," as "Merchant's" Portia. McGillis is getting married, then coming to Washington after her honeymoon.

Meanwhile, there will be duelling "Macbeths" in the area: Glenda Jackson and Christopher Plummer, two of the scariest actors in two of the Bard's most ruthless roles at Baltimore's Mechanic Theater, through February 21, before a Broadway run. Immediately following that production (February 22 to April 10), Shakespeare Theater artistic director Michael Kahn directs Franchelle Stewart Dorn as Lady MacBeth, Philip Goodwin as Mr. Macbeth, and T. J. Edwards as Seyton. The cast also includes Andrew Prosky, actor Robert Prosky's son, as Donalbain.

At least he'll know his lines: One of the lead roles in "The Night Hank Williams Died," which opens February 5 at New Playwrights' Theater, is being filled by playwright Larry L. King himself. "Until a few days before rehearsals started, we hadn't planned to use Larry," says NPT artistic director Peter Frisch. "I don't know how he'd do as King Lear or in a part better suited to Dudley Moore," Frisch says, "but after holding extensive auditions in Washington and New York, Larry seemed like the logical choice for the role. His knowledge of West Texas, combined with his own special presence, make him perfect." King also played Sheriff Earl Dodd for 16 performances in the Broadway version of his "Best Little Whorehouse in Texas."

Realizing perhaps that we're ready to start thinking about summer, the thoughtful folks at the Olney Theater have announced their upcoming season. The slate starts off with Neil Simon's "Brighton Beach Memoirs" (May 18 to June 12), directed by John Going, who did such fine work with last season's record-breaking "Noises Off." Next up is the musical revue "Side by Side by Sondheim" (June 15 to July 10); John Guare's "The House of Blue Leaves" (July 13 to August 7); Bill C. Davis' "Mass Appeal" (August 10 to September 4); and "Pack of Lies" by Hugh Whitemore, whose "Breaking the Code" is now on Broadway. Call 924-3400 for subscription information.

Bulletin Board: Studio Theater has revised its spring schedule to include "Ah Wilderness!" to mark the centenary of Eugene O'Neill's birth (March 16 to April 17); and "The Mystery of Irma Vep," a Gothic melodrama spoof, in tribute to the late playwright and actor Charles Ludlam, a theatrical visionary recently lost to AIDS (May 18 to June 19) . . . Broadway rocks: First there was Jerry Garcia on Broadway. Now, coming up in March at the Warner is a Linda Ronstadt concert, titled "Canciones de mi Padre" and crediting theatrical designers Tony Walton and Jules Fisher, with sets and lighting, Michael Smuin as director. And in March, Madonna will appear in David Mamet's new "Speed the Plow," co-starring Ron Silver and Joe Mategna . . .

In Jean Luc-Godard's new movie "King Lear," Peter Sellars, playing Shakespeare, joins Burgess Meredith (as King Lear), Molly Ringwald (as Cordelia), Woody Allen (as the Joker) and Norman Mailer (as himself). The film is (loosely) based on the Shakespeare play (which didn't originally include Mailer) . . . Sir Richard Attenborough has contracted to direct a Broadway musical based on the life of Martin Luther King, Jr. Baritone Simon Estes is the star; the show is supposed to open in February 1989 . . . Because of a Canadian Actors Equity rule prohibiting the "H.M.S. Pinafore" company from doing 16 shows without a day off, the Monday performance has been rescheduled to February 7 at 1:30 p.m. Ticketholders for Monday's show should call 254-3670 . . ."Banjo Dancing" just celebrated its seventh anniversary at Arena's Old Vat Room -- with 1,684 performances, Stephen Wade's one-man show is still the longest-running show in the history of Washington theater.