More than 5,000 advocates of a nuclear freeze and contingents of opponents as well poured into Washington yesterday as the House Foreign Affairs Committee prepared to vote on a non-binding resolution calling for a mutual, verifiable halt in production of such weapons by the United States and the Soviet Union.

The resolution, sponsored by committee Chairman Clement J. Zablocki (D-Wis.), is expected to be reported out of the committee today, despite adamant opposition from the Reagan administration which contends that a freeze would result in Soviet military superiority.

Randall Forsberg, a leader of the Nuclear Weapons Freeze Campaign, told more than 1,000 activists at the Calvary Baptist Church here yesterday that the resolution would pass the House "with a comfortable majority" but is expected to fail by something under 10 votes in the Senate.

Forsberg said freeze advocates then will press for amendments to funding bills this year to prevent the testing of nuclear weapons if the Soviets refrain from testing. The votes on these amendments will reveal which members of Congress are giving "lip service" to a nuclear freeze and which are sincere, she said.

"Anyone can endorse motherhood, apple pie and a nuclear freeze," Forsberg said, pledging that the freeze movement will "make a decisive difference" in the 1984 elections.

The Zablocki resolution, which will be joined with one sponsored by Reps. Edward J. Markey Jr. (D-Mass.) and Silvio O. Conte (R-Mass.), calls on the United States and the Soviet Union to pursue a halt to the nuclear arms race, decide when and how to achieve a mutual verifiable freeze on testing, production and further deployment of nuclear warheads, missiles and other delivery systems, and incorporate negotiations on intermediate range missiles into the strategic arms reduction or START talks.

The freeze campaign will hold a rally at the West Front of the Capitol today at noon, the highlight of a day of organized lobbying by delegations from 43 states.

Meanwhile, the National Coalition for Peace Through Strength Coalition, sponsored by the American Security Council, has organized an anti-freeze rally on the East Front at the same time to "counter the freezenik demonstrators." Actor Charlton Heston endorsed the anti-freeze campaign's activities with a commercial on NBC's "Today" show yesterday.

At a seminar sponsored by her Saint Joan Peace Institute, conservative Phyllis Schlafly yesterday assailed the anti-nuclear position now under study by the U.S. Conference of Catholic Bishops. "The freezeniks have tried to wrap themselves in the Bible and read people who believe in defense out of the church," she said. "We're not going to do that. We believe we have the high moral ground."

The crowd at the Calvary Baptist Church was considerably older and more prosperous-looking than the "peaceniks" of anti-Vietnam war days. Many, like Joan Searles, a housewife from Toledo, became active through their churches. "I knew nothing about these issues until about a year ago," said Searles, a member of the United Church of Christ, and one of 150 Ohioans to make the trip.

There were also 40 Arkansans armed with the 1982 voting records of their two senators and four congressmen on eight issues, including the nuclear freeze resolution, which failed by two votes in the House last year, the MX missile, for which Congress deleted production funds, and the B1 bomber, for which funds were approved.

Some 600 freeze activists from Maryland signed up to lobby. Sen. Charles McC. Mathias Jr. (R-Md.) and Rep. Beverly B. Byron (D-Md.) are leaning against the freeze resolution. Two Maryland Democrats, Reps. Steny H. Hoyer and Michael D. Barnes, have endorsed the resolution, while Marjorie S. Holt (R-Md.) opposes it.

Some 200 Virginians joined the lobbying effort to persuade a delegation which generally opposes the freeze resolution with the exception of two freshmen Democrats, Frederick C. Boucher and James R. Olin, who have co-sponsored the Zablocki resolution. Sen. John W. Warner (R-Va.) is sponsoring an administration-endorsed measure that calls for arms reduction rather than a freeze.