After a day spent huddling over how to deal with the departure of cast member Megan Mullally from its Broadway revival of “Lips Together, Teeth Apart,” the Roundabout Theater Company announced it would delay previews of the show as the search for a replacement actress commenced.

Opening night remains April 29, the final cutoff for Tony eligibility for the 2009-10 season. Show’s three other cast members — Patton Oswalt, Lily Taylor and David Wilson Barnes — apparently remain attached.

Mullally left amid rumors of a conflict with one or more members of the creative team — led by helmer Joe Mantello (“Wicked”) — and, according to the Roundabout, in breach of her contract. A rep for the actress did not return calls for comment.

It’s not yet clear whether the Gotham nonprofit theater company would consider filing a grievance with thesp union Actors Equity, as producers of the Rialto revival of “Speed-the-Plow” did when Jeremy Piven left that production unexpectedly in late 2008.

Mantello (“Wicked”) has served as a frequent collaborator with “Lips Together” scribe Terrence McNally, directing Broadway productions of McNally plays including “Frankie and Johnny in the Claire de Lune,” “The Ritz” (in a revival produced by Roundabout) and “Love! Valour! Compassion!”

Roundabout’s decision to stage 1991 play “Lips Together” stemmed from a reading of the script directed by Mantello about three years ago, Roundabout a.d. Todd Haimes said.

Cast was two weeks into the rehearsal process when Mullally left. Previews, originally set to begin April 9, have been delayed indefinitely until a replacement actress is found.

The loss of Mullally (“Young Frankenstein”), an Emmy winner for “Will and Grace,” is not as damaging a casting setback as it perhaps would be for a commercial production. Because Roundabout is a nonprofit theater, its subscribers have already bought tickets to the show as part of their subscription fee, and will likely turn out no matter who’s in it. (Single ticket buyers hoping to catch Mullally onstage, however, will likely be deterred.) Ticketholders for cancelled previews will be rescheduled once the new start date is established.