Two freshmen U.S. senators are pressing for a confrontation with Roger L. Stevens, chairman of the Kennedy Center, over what they claim is the Center's "exclusionary" theatrical booking policy.

"It's my view that this situation has to change, and that's what I expect to have happen," Democrat Bill Bradley of New Jersey said Wednesday.

During Senate debate last week on a measure to resolve the Kennedy Center's muddy debt picture, Bradley described the Center as "an exclusive artistic club" and complained that "such notable American playwrights as Neil Simon and Sam Shepard" have never had their works performed there.

Stevens was out of town during last week's Senate debate, but responded angrily to the senators' charges in an interview yesterday. The Kennedy Center has never even been offered the chance to do plays by some of the authors the senators listed, Stevens said, adding that more than 80 percent of all the plays presented at the Center have been by American playwrights.

Both Bradley and Wyoming Republican Alan K. Simpson -- both members of the Senate Committee on Environment and Public Works, which oversees the Kennedy Center -- went into unusual detail in their criticisms last week. And Simpson, unlike Bradley, took Stevens on by name. He said that Stevens' "dual role" as Kennedy Center chairman and as producer (independently or under the Center's aegis) "must inevitably lead to serious conflicts of interest.

"It appears that European playwrights are afforded unwarranted favoritism over American playwrights," said Simpson, listing Simon, Shepard, David Mamet and David Rabe as playwrights neglected by the Center.

Simpson called for a "broadening of the selection process and perhaps increasing the number of persons who determine what is to be performed."

Stevens protested yesterday that the Center's Board of Trustees -- which includes half a dozen members of Congress and "some very tough cookies," in his words -- is consulted about each season in advance. Beyond that, he said, any form of committee management would be "chaotic."

In practice, Stevens said, he and executive director Martin Feinstein make programming decisions jointly, but "we're trying to find good things -- we're not trying to keep things out, contrary to what people say."

New York Democrat Daniel P. Moynihan, co-chairman of the ad hoc subcommittee on public buildings, has agreed to pursue the issue at least to the extent of inviting Center critics to an informal meeting, according to a spokesman in Moynihan's office. Stevens and other Kennedy Center officials might or might not be invited to such a meeting, said the spokesman, but Moynihan's office will submit written questions to Stevens in any case.

A common element in both Bradley's and Simpson's interest in Kennedy Center policies is their friendship with New York producer Emanuel Azenberg, a longtime critic of Stevens and the Center. According to Azenberg, Stevens has frustrated several attempts to present the plays of Neil Simon at the Center.

When Bradley was a forward with the New York Knicks, Azenberg worked for Madison Square Garden -- the Knicks' home arena. Simpson met Azenberg through a mutual friend, Paul Kriendler, who runs the 21 Club in New York.

"I've met a lot of people in the theater," said Bradley. "I was in a similar business for 10 years and I made a lot of friends." In addition, Bradley once produced a play, "The Poison Tree," which failed after several performances in New York, he said.

Simpson said he had always been interested in the arts, "and then I come to Washington and see the bill of fare and here we have all these English plays and English actors. When we put up 4.3 million bucks of the taxpayers' money [the proposed fiscal 1980 appropriation for the Kennedy Center's tourist-related operations], we ought to see American plays."

"I'm glad he's made himself such an expert in his short time in Congress," was Stevens' response.

Another issue raised by Bradley was the absence of subscription series in recent years at the National Theater, which the Kennedy Center has been booking since 1974. Bradley claimed that Kennedy Center officials apparently had discouraged the idea of putting shows at the National on a subscription basis "to avoid competition with the highly successful series at the Eisenhower Theater."

The subscription series Bradley referred to is administered by the Theater Guild, and entitles playgoers to see 10 productions a year. All 10, in recent years, have been performed at the Kennedy Center, a situation which Chairman Stevens attributed to the difficulty of getting strong attractions for the National.

In addition, Stevens pointed out, a subscription series means that shows have to be booked ahead well in advance for definite runs. There have been a number of last-minute bookings at the National; and some shows such as "A Chorus Line," have stayed for long runs on the strength of their box-office performance.

None of the National's attractions appear on the 1979-80 subscription series, Stevens explained, because "we haven't got anything booked that amounts to anything." But he said the National, which used to account for most of the plays on the Theater Guild subscriptions before the Kennedy Center was built, may be included again.

"There's no reason for not doing it now," said Stevens, apparently referring to the resurgence of the downtown area surrounding the National.