Planning some extended family dinners over the holidays? Worried that folks might not get along, that festering tensions might surface, that people might get tipsy and say too much?

Well, here’s an idea: First, go see “August: Osage County,” the blistering film adaptation of the Pulitzer-winning Tracy Letts play starring Meryl Streep and Julia Roberts.

Because once you’ve witnessed the rollicking, vicious family dinner that’s the dramatic centerpiece of this movie, you’ll know you’re safe. No family meal of your own will ever seem truly unpleasant after you’ve witnessed this movie.

It is, of course, delicious that the most biting of these insults come from the mouth of the one and only Streep, who holds absolutely nothing back in a performance that could be called showy — except that’s it’s so compelling, and also deeply faithful to the script. Violet Weston, the 65-year-old matriarch of an Oklahoma clan, is simply one of the most spectacularly damaged characters in memory. And as written by the hugely talented Letts, who has both playwriting and acting Tonys to go with his Pulitzer, she’s someone you’ll want to meet — if only once.

Not that “August: Osage County,” directed by John Wells, works best as a movie, even with a screenplay by Letts himself. Those who saw the 2007 Broadway production will likely recall a nearly perfect theatrical experience.

It feels less naturally suited to film, though if you haven’t seen the play, you might not notice. And a brief final scene feels tacked on for cinematic purposes. But these are not fatal flaws.

Virtually all the action takes place in one home, in the heart of the Oklahoma plains, stifling in the August heat. It belongs to Violet and her husband, Beverly, a 69-year-old poet and raging alcoholic. “My wife takes pills and I drink,” he says. “That’s the bargain we’ve struck.”

And, boy, does Violet take pills. It’s a shock to see the regal Streep looking this way: wrinkled and pale, with a craggy fuzz of gray hair peeking out of a dark wig, a result of chemotherapy for mouth cancer.

Extended family is summoned home when emergency strikes: Beverly’s disappearance. All are forced to sit together, talk together, eat together, and of course face some serious family truths.

Margo Martindale is absolutely pitch-perfect as Violet’s sister Mattie Fae, at once boisterous, flighty, warm and witheringly insensitive to her awkward adult son, Charlie (Benedict Cumberbatch.)

Also wonderful is Chris Cooper as Mattie Fae’s long-suffering husband, and Julianne Nicholson as the lonely and misunderstood Ivy, one of Violet’s daughters.

Much depends, though, on the dynamic between Violet and daughter Barbara (Roberts), who’s in the throes of a disintegrating marriage. This is one of the meatiest roles Roberts has had in a good long time, and she handles it with an admirable lack of vanity. Gone is that high-wattage Roberts smile. Barbara is weary, bitter, and, at times, shrewish.

Watch her in that dinner scene, trying to dodge her mother’s verbal missiles, until she no longer can. Come to think of it, watch absolutely everyone.

And then plan your own family dinner, secure in the knowledge that it could never, ever be as bad.