The next-to-last episode of the series will feature Peters as Karen's (Megan Mullally) sister, reports Zap2it.com. Josh Lucas will also guest on that episode of the series, which airs on NBC-TV Thursdays at 8 PM ET; check local listings.

"Will & Grace" will end its lengthy run on NBC this season. In addition to Mullally, the comedy also stars Eric McCormack and Debra Messing in the title roles with Sean Hayes as Jack. Harry Connick, Jr., currently on Broadway in The Pajama Game, is also a recurring character.

Bernadette Peters was last on Broadway in the acclaimed revival of Gypsy, for which she received a 2003 Tony Award nomination for her performance as Momma Rose in the Sam Mendes-directed production. She won her two Tonys for her performances in Andrew Lloyd Webber's Song & Dance and Irving Berlin's Annie Get Your Gun, and she has also starred on Broadway in Mack & Mabel, On the Town, Sunday in the Park with George, The Goodbye Girl and the original production of Stephen Sondheim's Into the Woods.

Peters' newest recording, "Sondheim, Etc., Etc.—Bernadette Peters Live at Carnegie Hall (The Rest of It)," hit stores on the Angel Records label last summer. She will appear in concert at Lincoln Center's Avery Fisher Hall May 1.

For more information visit www.nbc.com/Will_&_Grace.