Roberts and Streep received best actress nominations for the Golden Globes and Screen Actors Guild awards - Streep, for lead actress, Roberts for supporting. And SAG nominated the entire cast - Abigail Breslin, Chris Cooper, Benedict Cumberbatch, Juliette Lewis, Margo Martindale, Ewan McGregor, Dermot Mulroney, Julianne Nicholson, Sam Shepard, Misty Upham and Roberts and Streep - in its outstanding performance by a cast category, the Hollywood guild's equivalent of a best picture honor.
Streep is Violet Weston in the John Wells-directed take on the 2007 play. She's the malignant matriarch presiding over an unhappy family reunion. She pops pills, puffs cigarettes, and has an unkind word for everybody. Oh yes, she has cancer, too.
Roberts is Barbara, the daughter who's moved away and married but who finds herself in the grim throes of a breakup. (Her husband, McGregor's Bill, has found another, younger, woman.) Barbara and Violet stare daggers at each other; it's all contempt, and painful memories, between them.
"The whole time we were shooting," says Roberts, "I just pictured Violet in this kind of crow's nest on a boat, like she had this secret place where she could climb up and see everybody's goings-on, all the conversations, and just collecting all that information to slaughter everybody with. . . . She's vicious!"
Roberts says she was undaunted by the prospect of working with Streep, with her 17 Oscar nominations, her three Academy Awards, her legendary ability to transform, to inhabit a role.
"She's amazing," offers Roberts, who has three Oscar nominations and one win (for Erin Brockovich). "But it's not daunting to be in Meryl's presence, to work with her, because she's so inviting. She doesn't hold you away to witness. She invites you into her orbit.
"It takes a little time to get your bearings when you're that close to her all the time, but she really does everything that she can in a very authentic way. . .. She makes you comfortable."
Set in small-town Oklahoma - "in the middle of nowhere close to anywhere" as Roberts nicely puts it - August: Osage County is an actor's marathon, a gabfest of finely tuned phrases. The actress says she and her castmates were constantly running lines with one another, rehearsing, reconsidering their scenes.
"I would come home some nights with no voice from screaming all day," she recalls. "But the amount of work we had was a saving grace, because you couldn't really allow yourself to collapse into thinking how sad and mean it all really is."
Sad and mean are not words that define Roberts, who has ventured to dark places in a few of her films ( Sleeping With the Enemy, Closer, the more tortured stages of the journey of self-discovery that was Eat Pray Love) but whose screen persona is generally sunny, saucy, plucky, resilient.
So wrapping her head around the character of Barbara, with her control issues, her coldness, her philosophy of dread, was . . .
"Well, actually, it was harder than I had anticipated," she says, laughing. "Because I think that, for me, at the center of all things is a true sense of optimism and happiness. And that just can't be found in this circle of people. . . . So it was challenging to try to find who [Barbara] really is, as opposed to just saying, 'Well, I'll go in there and I'll just start yelling and I'll yell all this stuff, and seem really mad.'
"There was a deeper value to it than that, in understanding those places and where they came from and how desperate and lost she is . . . It was like trying to do this truly crazy math, just to figure out each equation of why, and what, this person does, and how it makes you react to them. But what are you really feeling? And it got very complex."
Letts, the playwright and actor (he's Sen. Lockhart, a key player in the just-ended season of Showtime's Homeland), marveled at Roberts' work, and how she found layers of meaning, and emotion, in his words.
"She's a great actress," Letts observed in a separate interview. "And I feel silly saying this, but I said to her at one point, something along the lines of 'You should do this more often.'
"And here she is, one of the biggest movie stars in the world, and I'm saying, 'you should do this more often - act. You should act more often.'
"And her response was very quick, and very genuine. She said, 'Things like this don't come around very often. Scripts like this aren't exactly crossing the desk every day.'
"And that's a shame. She should have more opportunities."
Maybe she will. Roberts, 46, just wrapped work on the screen adaptation of Larry Kramer's award-winning AIDS drama The Normal Heart. She plays Emma Brookner, the physician (and polio survivor) who's on the front lines when the AIDS epidemic hits. The HBO movie was directed by Ryan Murphy, who steered Roberts through Eat Pray Love.
"I have the coolest job, I really do," says Roberts, who is married to Daniel Moder, a camerman she met when she starred in the 2000 release The Mexican. The couple has three kids.
"And at the end of the day, you go home to the light, and have all the more appreciation for that. That's one of the upsides to going through all the Weston mire - is to go home and realize, 'Oh wait, my life's not like that!' "