EXCLUSIVE: Dermot Mulroney is heading to Oklahoma. Joining the cast of August: Osage County, the actor will be going to the state this fall to start filming on the John Wells-directed film. Mulroney will play Steve in the adaptation of Tracy Letts’ 2008 Pulitzer Prize winning family clan play. Steve is the not-quite-who-he-seems businessman fiancé of Karen, the self-deluding youngest daughter of the family. Juliette Lewis plays Karen. August: Osage County reunites Mulroney with his My Best Friend’s Wedding co-star Julia Roberts. The Oscar winning actress plays Barbara, the daughter of Violet, played by Meryl Streep. Abigail Breslin plays Barbara’s disgruntle daughter, Jean. Margo Martindale recently joined the film too as Violet’s sister Mattie Fae. George Clooney and Grant Heslov are producing along with Jean Doumanian, Steve Traxler and Claire Rudnick Polstein. The Weinstein Co. is financing and distributing August: Osage County. Mulroney is repped by WME and attorney Barry Tyemann.

Related: ‘August: Osage County’ Adds Margo Martindale

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