According to the New York Daily News, the casting for “August: Osage County” has been finished with the latest addition of Julianne Nicholson as Ivy Weston, as the film is about to start shooting next week. Tracy Letts’ sprawling family saga “August: Osage County” starts filming on Monday. Asked how he whittled down his 3 1/2 hour play for the big-screen, he told me: “I was doing rewrites a couple nights ago.” Asked about his role in picking the cast in the film directed by “ER” alum John Wells, Letts admitted it was minimal. “I don’t know how much they listen to me,” he said, adding that he’s pleased with the cast headed by Meryl Streep as Violet, the mad matriarch. Julia Roberts plays her eldest daughter, Barbara. “The ironic thing is that the more successful a play is the more likely it is that actors will be shunted aside for movie stars. That’s the way it is.” Playing Roberts’ sisters are Juliette Lewis as Karen, and Julianne Nicholson as Ivy, Letts told me. Letts was in Oklahoma on Monday for the first table read. “It is the only day in the entire process I’m able to be there. They asked lots of smart questions.”