MOSCOW, JULY 4 -- American and Soviet rock groups teamed up on stage for the first time here today, mixing Russian folk tunes with rock and roll and -- with a stroll down memory lane -- bringing peace activists from both countries to the end of a long march.

Featuring an afternoon of oldies from the Doobie Brothers, James Taylor, Santana, Bonnie Raitt and other rock artists, the open-air concert gave Moscow and the crowd of 18,000 at a 25,000-seat sports stadium here a rare glimpse of the mood marking Independence Day a continent and an ocean away in the United States.

The concert, sponsored by the Soviet Peace Committee, the nation's leading official peace organization, celebrated the conclusion of a march that American and Soviet antinuclear weapons activists started more than two weeks ago in Leningrad, 450 miles from Moscow.

The crowd was motley -- thousands of young Soviet elite, members of the Komsomol, or young Communists, tourists, journalists and 230 American peace marchers from places such as Laguna Beach, Calif., Cambridge, Mass., and Portland, Ore. Tickets to the concert were free and were distributed through unions and the Soviet Peace Committee. The general public was not invited.

It all started with a mass release of doves and toss of roses and turned into a day of Fourth of July fun, with James Taylor singing "Fire and Rain" and other oldies, the Doobie Brothers singing "Jesus Is Just All Right" and crowds alternately dancing and frolicking around the massive sports stadium where the festivities took place.

It was the first major concert here in which Soviet and western groups appeared side by side, with the Russian folklore ensemble Rusichi and the rock group Autograph leading the Soviet part of the program.

The Soviet organizers added their touch to the festivities, too: Members of the Soviet Peace Committee made welcoming remarks. The Soviet flag -- a hammer and sickle against a red background -- was displayed next to the Stars and Stripes. And men in dark suits were dispersed through the crowd, carrying umbrellas even though the sun sparkled in the sky.

The appearance here of the Doobie Brothers, whose rock music tradition dates back to the 1960s, added to the feeling that Moscow is becoming a bully pulpit for American politicians and entertainers.

Earlier this week, 1960s black political activist Angela Davis signed autographs in one Moscow park, surrounded by a sea of American peace marchers, while former Democratic president Jimmy Carter met with Kremlin leader Mikhail Gorbachev.

This summer has brought three major peace rallies or conferences to the Soviet capital, including an international physicians' conference last month, a women's conference last week and this week's peace march. They have all drawn dozens of Americans, many of whom came out solidly in favor of Gorbachev and his reform program, in addition to promoting their own causes.

For the most part, the crowd seemed to like what they heard. Though the Soviets filling the bleachers never clapped or cheered, others down in the stadium with foreigners explained that it is not in the tradition of Soviet rock audiences to break out in jubilation at the sound of rock.

The concert punctuated a peace march of some 400 Americans and Soviets that began in Leningrad May 18 and ended here Wednesday.

Rather than walk the entire 450 miles, the marchers were bused through some areas and walked through others. In the end, the walk had amounted to about 150 miles, they said. Some were veterans of major marches in the United States, including last year's Great March for Peace from Los Angeles to Washington. Others marched here for the first time.

With the Doobie Brothers and other groups blaring in the background, some of them handed out praise in big doses -- to their Soviet counterparts in the march, to Gorbachev, to the Russian people. "Gorbachev is the only sane leader in the world," said audience member Helen Caldicott, an Australian antinuclear activist based in Seattle.

"He's like Jesus. He just keeps giving out good things like arms control proposals and {getting} hit with rejections," she said.

Added Gerda Lawrence, a peace marcher from Los Angeles, "We're overrunning the enemy mentally. People-to-people contacts are helping to combat weapons. It's a great way to spend the Fourth of July."