Director John Wells created an incredibly believable family in his new film "August: Osage County" -- and it felt like one off-screen too, the all-star cast said Tuesday.

Based on playwright Tracy Letts' Pulitzer Prize-winning play, the production brought together Meryl Streep as a mother of three daughters portrayed by Julia Roberts, Julianne Nicholson and Juliette Lewis.

It also stars Abigail Breslin, Chris Cooper, Dermot Mulroney, Ewan McGregor, Benedict Cumberbatch and features a cameo by Sam Shepard.

At its premiere at the Toronto film festival, the cast recalled getting together for family-oriented activities like potluck dinners and to watch television.

"It sure helped to give a family feel," Cooper said.

Their off-screen efforts paid off and are particularly noticeable in an extended dinner scene, which took three and a half days to shoot.

"It was my favorite scene and my favorite days on the set because everybody was there," Wells said.

For Roberts, "to have a bedrock of who you are, that's what it's all about."

Of course, families can also be dysfunctional and that, too, comes across in the film.

A dinner scene after a funeral is marred by insults and indignation, culminating in Roberts's character lunging at Streep's.

"The Westons are hardly the Waltons," the happy American television family of the 1960s, said one blog review.

"I don't have to be angry for 10 more years, I got it all out" in the film, quipped Roberts.

Lewis said she relished acting in the film because of "the layers of humanity, the ugly, the beauty, the pain, and all that delicious stuff" typical of real family dramas.

"It's not superheroes (a cinema trend of late)... so it's a real honor to expose this kind of human frailty and dysfunction and all the inner workings," she said.

Other films at the festival exploring less traditional family dynamics include Stephen Frears' "Philomena," starring Dame Judi Dench in a tour de force performance as an elderly Irish woman searching for a child she was forced to give up for adoption.

Nicolas Cage, meanwhile, plays an ex-convict with a temper who struggles to father a young boy in David Gordon Green's "Joe."

"These are not 'sit around the dinner table and discuss with mom, dad and the kids' type of family stories," festival boss Cameron Bailey told AFP.

"They show people struggling to find new forms of family and maybe that reflects some greater volatility in our society."