Twentieth-century suburbia in New Zealand is not radically different from 20th-century suburbia in the United States, if one is to judge from "Middle Age Spread," a play by New Zealander Roger Hall that is currently receiving its American premiere at the Source Theatre.

There, as here, marriages settle into the rut of routine. A mild form of discontent seems to pervade the air, and mates cheat on one another. At dinner parties, people talk about job promotions, the new blinds, the merits of jogging, the erosion of the work ethic, the stupidity of government handouts, the laziness of the younger generation and teen-age pregnancies.

Unfortunately, this doesn't make "Middle Age Spread" universal as much as it dooms the evening to a certain triteness. If the program and a few passing references didn't indicate otherwise, the action could be unfolding in Reston.

The play has enjoyed considerable success in its homeland and subsequently in London, and has also been made into a movie. So perhaps something is missing from the Source production. I'm not sure what. Hall has been touted as "New Zealand's answer to Neil Simon," a description that totally eludes me. If comparisons must be made, "Middle Age Spread" seems to be a blend of very pale Edward Albee and very pale Alan Ayckbourn.

What we have are three middle-aged couples gathering--largely against their collective will--for a dinner party. The host, Colin (Richard deLaubenfels), has just been promoted to principal of what sounds like a fairly shoddy school. If he doesn't see it as much of a triumph, his wife, Elizabeth (Beverly Brigham Bowman), apparently does. The chatter is amusing in a vaguely satirical way at first, although there is clearly an undercurrent to the festivities. In a series of flashbacks that interrupt the dinner at critical junctures, we learn why.

Despite his milquetoast ways, Colin is in the throes of a mild mid-life crisis and has recently had an affair with Judy (Dianne Couves), one of the married teachers in his school. Just as the two had decided to call it quits, however, snide, cynical Reg (Dick Harrington) burst into Judy's apartment and caught them in flagrante delicto.

And now here they all are--Colin and Elizabeth; Judy and her spouse, Robert; Reg and his spouse, Isobel--sipping wine and nibbling hors d'oeuvres. By the time the dinner party reaches dessert and coffee, Reg has blabbed and everyone is uncomfortable.

"What do we do now?" asks Elizabeth, after the guests have beaten a retreat. "What we do, Elizabeth, is the dishes," replies Colin. Perhaps the exchange carries greater punch in New Zealand.

A troupe of top-notch actors might be able to coax more substance (or more humor) out of Hall's dialogue than the Source company does. But the six players director Bart Whiteman has gathered together stick pretty much to the surface of things and the surface seems awfully flat in the long haul. Whiteman has broken up the scenes with videotapes of the various characters in the great outdoors. They are seen jogging for the most part, which may be interpreted as trying to keep up with the Joneses. Then again, they may be just jogging.

As for the set--two bedrooms and a living room, furnished with lots of modern furniture--it suggests the upwardly mobile aspirations of its inhabitants. But in Source's tiny quarters, it also suggests an overstuffed showroom. Maybe things are getting cluttered in New Zealand, too. MIDDLE AGE SPREAD. By Roger Hall. Directed by Bart Whiteman. Set, Bart Whiteman and Steve Siegel; lighting Bart Whiteman and Eric Annis. With Beverly Brigham Bowman, Richard deLaubenfels, Joan Kelley, Dick Harrington, Dianne Couves, Stephen Wallace Haines. At the Source Theatre through June 18.