Writer-director Joe Swanberg, a prolific maker of so-called mini-budget mumblecore films about the relationships of young modern twenty-and-thirty-somethings, makes a significant stride forward with his latest, a kind-of romantic comedy involving two workers at a Chicago micro-brewery who’ve long been good friends but appear fated to be considerably more than that. The alcohol flows freely in “Drinking Buddies,” but happily not all the high spirits are of the liquid variety.

Kate (Olivia Wilde) is the marketing honcho for the brewery run by Gene Dentler (Jason Sudeikis), and Luke (Jake Johnson) is the foreman on the production end. The two share an easy familiarity, joking and lunching together, and they often accompany other workers to a neighborhood bar after work for a few drinks, a game of pool and more friendly joshing. But each is committed to somebody else. Luke has a live-in girlfriend, sweet Jill (Anna Kendrick), and Kate a serious boyfriend in Chris (Ron Livingston), an older, quite successful fellow.

The crux of the admittedly loose plot comes on a trip the four take together to a rustic vacation cabin Chris has in the Michigan dunes, where walks, some fraught conversation, and a midnight jaunt to a nearby beach test the current romantic line-up. But Swanberg wisely doesn’t let matters work themselves out in the clichéd, mechanical fashion of most Hollywood comedies. Instead he allows situations to develop in unexpected ways without payoffs a studio product would encourage us to anticipate. And he invests the characters at the center of things with surprising layers of feeling—not simply Kate and Luke, whose moves toward one another are invariably followed by their inching away, but also Jill and Chris, whose fears and uncertainties drive what happens as much as their current partners’ do.

The cast respond beautifully to the sense of spontaneity and casualness that Swanberg provides in both his writing and his direction. Wilde is the undoubted sparkplug, making Kate both driven and endearing. But Jackson matches her with his charming gruffness (as well as being utterly convincing in a sequence in which he injures his hand while helping Kate move a couch). Kendrick conveys Jill’s insecurity about what the future holds without slipping into broad caricature. And Livingston, who often comes across as merely smarmy in his film roles, adds to his more than capable work as the husband in “The Conjuring” with a turn that captures Chris’ anxiousness over where his life is heading. Together they make up an ensemble that reflects the doubts and longings of real people rather than the reactions of the usual predetermined cardboard figures of romantic comedy.

Though the factory ambience of the brewery is nicely caught, Ben Richardson’s cinematography, while nicely unfussy, fails to register a real sense of the larger Chicago locale, and the Michigan sequences are visually anonymous as well. But generally the middle-class environment is well caught in Brandon Tonner-Connolly’s production design, and Amanda Ford’s costumes are certainly dowdy enough to be convincing.

There are times in “Drinking Buddies” when the alcohol consumption is so conspicuous that you fear Kate and Luke might be destined to do a variation of “Days of Wine and Roses” as a sequel. But the buzz being enjoyed by viewers comes from different sources—sharp writing and appealingly natural performances.