Gastronomically, at least, they may be theater's newest odd couple: Roger Stevens and Joseph Papp.

"Nothing too gourmet," Papp said last night after the opening at the Kennedy Center of "The Art of Dining."

You just have to look at me," interrupted his co-producer, Roger Stevens, "to see how I feel about food."

The slightly built Papp and the wellpadded Stevens presided at a post-theater dinner in the new Four Seasons Hotel where the menu was a recreation in part of that figuring in the theatrical production.

A tab variously said to be picked up by (1) the co-producers, (2) the Kennedy Center (3) the Kennedy Center and the hotel, added up to $39 per person plus drinks.

For starters, it featured a mussel soup call Billi Bi, roast duckling with Armagnac-saturated cherries, watercress salad and a desert that, translated, meant floating island. Wines were plentiful, and as the evening progressed, increasingly unpronounceable.

The guest list was a selection of Washington regulars from Capitol Hill, the White House and the arts community. In addition, the entire cast of the play, as well as the author, Tina Howe, were seated at the candlelit tables, where a white-gloved waiter hovered solicitously.

It may well have been the ultimate in dinner theater: a play about a gourmet restaurant followed by a meal to match. But lest anybody think it was a mere play about food, Papp was ready to set the record straight.

"It's really a serious play, I selected it because it is a touch play, and because Tina Howe writes several layers at a time -- it's slightly poignant and beneath is a strata that is personal. In fact," Papp contined, "I think the play is almost cataclysmic."

Howe, a slender, almost wraithlike figure, hardly touched her post-theater dinner."I'm a writer, not an eater." she told stevens' wife, Christine.

The number of non-eaters in the elegant ballroon included most of the cast.

"I eat eight shows a week," said Margaret Whitton, who used to "love chicken salad from any greasy-spoon. But since I started this play, I've lost 10 pounds."

Kathy Bates, who is paid to make a pig out of herself in the play, left that real-life pleasure to Mr. Pip, her 4-month-old Yorkshire terrier, during the party.

Guests arrived from the Kennedy Center almost ready to eat the elaborately printed menus.

"I was famished," said Martin Feinstein, Jayne Ikard, whose husband Frank, is a member of the Kennedy Center's board of trustees, insisted that the only reason the on-stage French culinary activities didn't make her hungry was that "I like Italian food."

Suzanne Collins rather sensuous interpretation of creating Hollandaise sauce came in for some raves.

"There was a kind of gusto there," said Jeannete Williams, for want of a better word. "I also like the way she talked to the (dead) fish."

"I must be a real dummy," said Collins with the most convincing innocence, "because I didn't realize I was being sexy." Representing the Senate at the seated dinner were Charles Percy (R-Ill.) and Harrison Williams (D-N.J.). Gordon Stewart, presidential speechwriter, and Jack Watson, presidential assistant for intergovernmental affairs, took time out from presidential affairs.

"Your part has gotten high praise," Stewart told Watson, alluding to Jimmy Carter's State of the Union message currently in the works.

"We're trying to get it together enough so he can take it with him and play with it under the Christmas tree," Stewart said.