It's funny how familiar something can be that you've never seen before.

Perhaps that isn't quite the case with "Ah, Wilderness!" Eugene O'Neill's one comedy is well known and gets staged from time to time, but not as often as you'd expect because of its large cast (15) and three sets.

No matter. Its image of family-centered, straw-boatered, pre-World War I America is as familiar as a cliche or a classic. And its story of the coming-of-age of a sensitive teen, reclaimed from rebellious dissipation by an understanding family, is one re-told in popular art from William Inge to Neil Simon, from Norman Rockwell to "Happy Days."

The professional Playhouse Rep presents a very fine "Ah, Wilderness!," proving it much more classic than cliche. It has a capacious, measured, luminous self-assurance that makes it feel like a wise window on a world of nostalgic desire.

This assurance begins with Michael Thomas Essad's set, itself a hymn to turn-of-the-20th-century small-town America, with its comfortable living and dining room, embowering tree and upper window shining with dreamy light. Director Robert Miller begins with a family tableau and the yearning words of Randy Newman -- "sing a song of long ago" -- with any potential ironies thoroughly shuttered.

On this July 4 and 5 in 1906, Richard, 17, is in trouble for sharing his advanced ideas, culled from Shaw, Wilde, Swinburne and Ibsen, with his innocent girlfriend. He rebels and goes to a local dive with a floozy, but real dissipation is avoided. Most important, Richard has the immediate support of his understanding father, owner of the local newspaper and thus more progressive than the town average, and his worried, querulous but warmhearted mother.

It's a full family portrait, including an older brother swaggering with Yale undergrad smarts; younger sister and brother; Uncle Sid and Aunt Lily, who might someday be a couple if Sid didn't periodically fall off the wagon; and the inevitable Irish maid. Add in Richard's girlfriend, her stern father and the denizens of the tavern Richard visits and you get a rich panorama that no contemporary playwright would dare to write.

This is, of course, the flip side of the much darker family portrait of O'Neill's other play set in what he remembered of his family's New London house, "Long Day's Journey Into Night." This is the family that he probably wished he had had.

There are glimpses of that other world in the tavern scene, with its desperate floozy, angry Irish barkeep and flesh-hunting salesman -- and also some of the awkward tough-guy lingo that clutters up much of O'Neill's work. And Richard's scene with his girlfriend is a kind of comic parody of the more tormented equivalent in "Hedda Gabler." But the play is mainly serene and embracingly comic.

Making it work is Miller's very capable cast, led by the masterfully un-cliched father of Larry John Meyers. Penelope Lindblom dithers affectingly as his wife, and Phil Winters is all restraint and pathos as the amusingly inebriated Sid. Joel Ripka stars as Richard, and though he doesn't have the palpable youth of a real teenager, he never overstates.

It's good to see City Theatre's Kellee Van Aken back on stage as the disappointed but resilient Lily, and Erica Cuenca shines as young Mildred. Beyond these, there are accomplished actors filling out small roles with dimension: John Amplas as the interfering father, Erica Highberg as the surprisingly sympathetic floozy and several more.

At 2 and a half hours (including two intermissions), "Ah, Wilderness!" takes its stately time. But it has to. This is a play to savor.

Its title comes from the "Rubaiyat of Omar Khayyam," another of Richard's risque readings, so it's not surprising that the subject is love -- not erotic love but the familial love O'Neill fantasizes for us all in his forgiving dream of a midsummer night long ago.