For all the high-profile actors assembled in the upcoming drama "August: Osage County" — including Meryl Streep, Julia Roberts, Chris Cooper, Ewan McGregor and Benedict Cumberbatch — the real star of the film may be the language, written by Tracy Letts, who adapted his own Pulitzer-winning stage play.

At a recent installment of the Envelope Screening Series, director John Wells and some of his cast talked about the importance of language in the Oklahoma-set family drama.

"My concern was that the best possible actor for each part be in the part because the material is complicated, it's difficult," Wells said. "It requires a significant amount of concentration. The language seems as if it's simple; it's not actually simple. It's beautifully written and complicated. And so I needed to make certain, I wanted to be positive that in every single role the most talented actor who was appropriate for the role was in that part."

Many of the cast members embraced Letts' complex language. "I found it very easy to learn," said Margo Martindale. "There's a lot of music in it, so that makes it easy. It was easy to my ear and easy to my brain."

VIDEO: Watch 'August: Osage County' cast, crew discuss film

Cooper agreed, adding, "I think it has always been [that] poorly written material is hard to memorize."

For Wells, another form of language helped sell that the characters are blood relatives: body language.

Wells said, "The actors who were part of the family … they studied each other, studied what they were doing, what Meryl was doing — how was she making choices about how to move her head, how was she going to laugh, what was she going to do. And the actresses who were in the family spent time studying what that was and then did it. Spending that time together, studying each other, was a huge part, I think, of what makes it feel as if they really are a family."

For more from the cast and crew of "August: Osage County," including Julianne Nicholson on one of the film's most challenging scenes, watch the full video above, and check back for daily highlights.

ALSO:

A turn, a snap, a fall: Signatures of the stars

Films inspired by true events walk a tricky line

At the Gotham Awards, non-folksy tributes, then a folkie win