Cullum, according to The New York Times, will play the role of Beverly Weston for eight performances while Michael McGuire, who currently plays the Weston patriarch, is on vacation.

John Cullum earned Tony Awards for his work in On the Twentieth Century and Shenandoah. His extensive stage career also includes On a Clear Day You Can See Forever, Urinetown, Man of La Mancha, Aspects of Love, 110 in the Shade and the recent Lincoln Center mounting of Cymbeline. Cullum is well known for his Emmy-nominated work on television's "Northern Exposure."

The Broadway run of Tracy Letts' Tony Award-winning, Pulitzer Prize-honored August: Osage County hit 300 performances Aug. 13. The darkly comic play about a dysfunctional Oklahoma family and its truth-tellin', pill-addicted matriarch, is the longest-running play of the 2007-2008 season.

Directed by Tony, Drama Desk and Outer Critics Circle Award winner Anna D. Shapiro, August: Osage County plays the Music Box Theatre, where it moved following its Broadway debut at the Imperial Theatre (next door).

The Steppenwolf Theatre Company production of the play premiered in Chicago in summer 2007, and producers swooped in to take the show to Broadway.

August: Osage County currently stars Robert Foxworth, Kimberly Guerrero, Brian Kerwin, Madeleine Martin, Mariann Mayberry, Amy Morton, Sally Murphy, Estelle Parsons, Molly Regan, Jim True-Frost, Troy West and Frank Wood.

The three-act, three-and-a-half hour drama plays Tuesdays-Fridays at 7:30 PM with matinees on Wednesday and Saturdays at 2 PM, Saturdays at 8 PM and Sundays at 3 PM. Tickets can be purchased at Telecharge.com or by calling (212) 239-6200. Outside the New York area, call (800) 432-7250.

The Music Box Theatre is located at 239 West 45th Street.

For more information visit www.augustonbroadway.com.