The Kennedy Center for the Performing Arts, apparently anxious to bring a more adventurous brand of theater under its imposing roof, has begun to parcel out blocks of time at the new Terrace Theatre to a range of outside groups.

Washington's Folger Theatre Group will stage two plays - probably new ones - at the Terrace Theatre next year, it was revealed at a joint press conference yesterday.

Kennedy Center Chairman Roger L. Stevens said afterward that he hoped to strike similar deals with the newly formed British American Repertory Company (BARC), and two New York-based groups, the Acting Company headed by John Housemand and the Public Theatre/N.Y. Shakespeare Festival headed by Joseph Papp.

The unheralded idea of a partnership between Papp and Stevens emerged as Papp acknowledged that he has been exploring prospects for establishing a company of his own in Washington. Beyond saying that it would not be housed in any existing facility, Papp refused to disclose any specifics.

Papp said yesterday that he would be in Washington today "and I'm sure it's for a serious purpose," he added mysteriously. "I don't travel for nothing."

In a conversation two weeks ago Papp seemed to set the stage for further developments here.

"If I were to be (in Washington), the company would have to reflect in many ways the city itself," he said. "The theatrical structure there is still functioning, I think, in an old-fashioned way. There's nothing that comes through that cuts through."

"It would be a different kind of the theater that doesn't exist there at president," said Papp. But he was careful to add that he would consult all of the existing Washington theater groups. and Mayor Marion Barry, before formalizing his plans, "I'm not coming as the champion who's going to show that Roger Stevens is junk and the Arena is bourgeois. That's not my thinking at all."

Papp said he and Stevens have recently discussed corproducing a new play called "The Art of Dining," by Tina Howe, which deals with a restaurant and a husband and wife "obsessed with food."

Producer Louis W. Scheeder said yester that the Folger's overall plans are to do Shakespeare's "Macbeth," "Twelfth Night" and "The Taming of the Shrew" at its home theater next season, plus John O'Keefe's 18th century comedy, "Wild Oats," Arnold Wesker's recent London hit "Love Letters on Blue Paper," and two as yet unchosen new plays.

The two new plays are the likeliest choices for the Terrace Theater, Scheeder said, although Stevens later interjected that they might choose a revival instead.

In any event, the two "plays-in-residence" at the Terrace will be regarded as integral parts of the Folger season, according to Scheeder, and their three-and-a-half week engagements are desinged to accommodate the same number of total patrons as an eight-week run at the smaller Folger.

The Folger will use its new arrangement to expand its subscription season from five to seven plays, and the two engagements at the Terrace will overlap with productions at the Folger's own facility on Capitol Hill. By simultaneoulsy extending the runs of some plays, Scheeder explained, he hopes to build the Folger's subscription audience from roughly 8,000 - which is all it can currently handle, he said - to as many as 10,000 or 11,000.

"It's a tremendous opportunity and it's exactly what this theater is desperately in need of," said Scheeder.Stevens called the plan a "mutally satisfactory arrangement for all of us."

The Terrace Theater not only has 513 seats - more than twice the number at the Folger - but a wider, deeper and taller work space, an orchestra pit whose floor can be raised to expand either the performing or the seating area.

Scheeder said the Terrace will offer his group the chance to play with "toys I've never had before." But he jested that after a decade of dealing with the Folger's colonnade-like auditorium he might find it necessary to install temporary columns among the Terrace Theater's seats to ease the shock of having unobstructed sightlines.

The Folger has been following a policy of running its Shakespeare plays for eight weeks each and its new plays for only six weeks, but the eight-week run will now become standard said Scheeder. Nevertheless, he said, the increase in ticket sales made possible by this shift will probably not be sufficient to cover the cost of mounting the two productions at the Terrace Theater. To make up the difference, the non-profit Folger group is in the process of raising an extra $75,000.

BARC, a newly formed company with an equal number of British and American actors and a performing agenda to be split between the two countries, will present a new (and still unwritten) play by Tom Stoppard at the Terrace Theater in September.

John Houseman's company is principally composed of graduates of the Julliard School's theater program. Its prodctions of "A Member of the Wedding" and the "The Three Sisters" have been seen here, at the Eisenhower and Ford's Theater respectively.

Papp, who originally made his name as the sponsor of free Shakespeare in New York Central Park, now runs a seven-stage complex in Greenwich Village, where he has launched, among other plays, "A Chorus Line," "That Championship Season," "Sticks and Bones," "Short Eyes" and "For Colored Girls . . ."

His multi-racial productions of Shakespeare have generated controversy during the current theater season, and Papp recently announced plans to establish a "Third World Theater Company" composed heavily of black, Hispanic and Orientaly actors. But "I don't just do plays with a minority angle," he said when asked about his interest in Washington, "I'd run out of plays."

Stevens said yesterday that the burden of booking the Terrace Theater as well as the Eisenhower had spurred the decision to invite more outside groups in. As a producer, he said, he was already as busy as he wanted to be without "sticking my fingers into the Terrace Theater, too."

No more than a third of the Terrace Theatre's over-all schedule will be devoted to plays. Stevens said that dance, music and opera programming will fill the remainder.