When it rains talent, it pours.

In a Broadway season that has already been blessed with two Tony-winning actresses (Christine Ebersole and Donna Murphy) matching or even surpassing their past musical efforts, plus a strong showing by two new faces (Lea Michele and Laura Bell Bundy), Audra McDonald has reclaimed her mantle as the era’s premier musical-theater actress.

Even when she’s miscast, as in the Roundabout’s capable new revival of “110 in the Shade,” Ms. McDonald is the anti-diva, incapable of singing a note or saying a word that in any way steals focus from or diminishes the material. Despite her effortless glamour, she has turned Lizzie Curry, a spinster in the making who’s “as plain as old shoes” and terrified of growing old alone, into a touching, forthright, and abidingly real creation.

If Lizzie’s name rings a bell, it may be from “The Rainmaker,” N. Richard Nash’s 1954 play about a mountebank who sweeps into a drought-plagued Texas town and, between promises of bringing “a good Old Testament wade-in-the-water and shoutin’-glory rain,” helps poor not-so-old Lizzie feel pretty with the help of a little roll in the hay. Despite its eyebrow-raising gender politics, “The Rainmaker” has shown itself to be a durable script and was revived successfully in 1999 with Jayne Atkinson as Lizzie and Woody Harrelson as Starbuck, the would-be miracle worker. Nash retooled the script himself for “110,” and the extended book scenes are quite strong. (Lyricist Tom Jones and composer Harvey Schmidt, making their Broadway debut, were arguably too deferential toward their collaborator, with some songs largely restating ideas that were already established through dialogue.)

Messrs. Jones and Schmidt are far better known for their smaller-scale efforts: “The Fantasticks,” of course, but also the two-person “I Do! I Do!” Their 1963 evocation of an insular Texas community clearly took a page or two from “Oklahoma!,” right down to its Agnes de Mille choreography. Notwithstanding Mr. Schmidt’s expansive, Americana-inflected harmonies, though, the two were no match for Rodgers and Hammerstein when it came to painting on a broad canvas.

“110” finds itself on firm ground when it focuses on Lizzie, Starbuck (Steve Kazee), and File (Christopher Innvar), the divorced sheriff who shares Lizzie’s aversion for emotional honesty. The choral sequences suffer from a jarring lack of specificity, however, and director Lonny Price exacerbates the murk with several anachronistic performances among the ensemble. Perhaps sensing this, Mr. Price has jettisoned one chorus number and added the pleasant if redundant “Evenin’ Star” for Starbuck.

Like the Roundabout’s last show in its Studio 54 space, a wan remounting of “The Apple Tree” starring Kristin Chenoweth, “110” is back on Broadway primarily because of the interest of a major star. But while Ms. Chenoweth unleashed her predictably polished shtick on her (admittedly slight) “Apple Tree” material, Ms. McDonald’s performance offers any number of delightful surprises. She tackles Lizzie’s crippling insecurity with fearless precision and then turns on a dime for a showstopper such as “Raunchy.” In this faux burlesque number, Ms. McDonald taps into a touching subtext of naiveté and even envy as Lizzie apes the flirtatious ways of her more brazen peers; her balletic approximation of a hip-swaying strut betrays her unseasoned past, adding poignant shading to the song without sacrificing an ounce of its comic potential. (The otherwise unmemorable choreography is by Dan Knechtges.)

By accentuating the failings of all three central characters, not just Lizzie’s insecurity, Mr. Price deftly minimizes the squirm factor of a woman closing Act 1 by begging God not to make her an “Old Maid.” Messrs. Kazee and Innvar provide sufficient emotional ballast to make Lizzie’s decision a believably difficult one. While the pair’s vocals don’t keep pace with Ms. McDonald’s (whose would?), Mr. Innvar gives File’s cloistered decency a welcome touch of grit, and a messianic-looking Mr. Kazee swoops into town like a hirsute Harold Hill, effectively conveying Starbuck’s enthusiasm but also his wanderlust. And Bobby Steggert is pleasant, albeit in a stock musical-theater characterization, as the naive baby of the Curry family. Only an overly broad Chris Butler, as Lizzie’s stern older brother, fails to impress.

Ms. McDonald is pretty much in a category of her own, with one exception — a 77-year-old man who has two tiny portions of two not particularly memorable songs. John Cullum, who was starring on Broadway before Ms. McDonald was born, offers a master class in character acting as H.C., Lizzie’s empathic father. He blends in at all times — he barely moves in “Raunchy,” although he’s the only other person on the stage — and yet it’s impossible not to factor into each scene where H.C. is and what he makes of the odd, potentially emotionally ruinous goings-on involving his beloved children.

Studio 54’s bifurcated pit-orchestra setup is as disastrous as ever, with half the musicians sitting on each side of the audience. And Santo Loquasto’s main set element, a giant retractable disc that conveys both the scorching sun and the hypnotic moon, allows for some haunting visuals but also some distracting logistics. But these qualms tend to fade into the background when “110 in the Shade” settles into its long, captivating book scenes or when Ms. McDonald wraps her exquisite soprano around songs such as “Love, Don’t Turn Away” or “Simple Little Things.” Simple little things are nothing to take lightly in a Broadway musical. When they’re being offered by women and men as gifted as Audra McDonald and John Cullum, they can be as restorative to a parched palate as an unexpected summer shower.

Until July 15 (254 W. 54th Street, between Broadway and Eighth Avenue, 212-719-1300).