Australian Wendy Turnbull, who lost to Virginia Wade, 6-1, 6-2, in the first round here last year, beat the Wimbledon champion today, 6-2, 6-1, to advance to the semifinals of the U.S. Open tennis championships.

Corrado Barazzutti, an unseeded 24-year-old Italian Davis Cup player, pulled an upset that was similarly surprising in its one-sidedness when he romped over No. 3 seed Grian Gottfried, 6-2, 6-1, 6-2.

Marina Navratilova, seeded No. 2 and considered to have the best chance of any of the women to dethrone 1975-76 champion Chris Evert, thumped French Open champ Mima Jausovec, 6-4, 6-1, and will meet Turnbull in the semis.

Turnbull, 24, and nicknamed "The Rabbit," is one of the quickest players in the women's game. She used her speed to good advantage and played steadily to oust Wade, who was impatient, sluggish and terrible off the backhand.

"I just concentrated on keeping the ball in play, not giving her any pace, and looped a lot of forehands high to her backhand. She likes to hit her backhand low and firm, so she didn't like what I was doing at all," said Turnbull.

Turnbull played smartly, slicing her backhand, moving Wade around, waiting for the 32-year-old Wimbledon queen - who won here in 1968 on grass, but has never been really comfortable since the surface was switched to clay in 1975 - to mistakes.

Turnbull used the drop shot to good advantage, and swept in to cover and hit forcing shots when Wade tried to retaliate.

Turnbull had beaten Rosemary Casals, 4-6, 6-0, 6-0, in the quarterfinals, and has now won 24 of 27 games in four sets from the No. 6 and No. 3 seeds. Ranked No. 13 in the computer ratings of the Women's Tennis Association, she was seeded No. 12 here.

Once considered a talented player who lacked only confidence, Turnbull has been playing much better tennis since she was traded from the World Team Tennis Boston Lobsters to the Cleveland Nets for Navratilova in midseason.

"It helped because I became the No. 1 singles player and got to play a lot of the top women," she said. "I learned a lot from that. I started to play the big points a lot tighter."

Today six games went to deuce - four in the first set, the first and last in the second - and Turnbull won them all. She showed no trace of nerves when the match appeared within grasp.

Wade saved two set points as she served at 2-5 in the first set, and one match point with a ripping backhand cross-court passing shot, but otherwise could not come up with a big shot when she needed it.

She had two break points in the first game of the second set as Turnbull hit an overhead long to 30-40 and double-faulted to a Wade advantage. But Wade netted a backhand return, hit a backhand volley long and punched a wild forehand folley on Turnbull's first game point.

Turnbull broke with a nice backhand drop shot winner at 30-40 in the next game, and calmly held her serve from there, breaking again in the final game as Wade hit a forehand return wide.

Navratilova and Jausovec were playing in the stadium court at the same time - the latest example of outrageously badn scheduling in this Open.

Navratilova broke to a 3-1 lead, Jausovec caught up at 3-3, and then Navratilova took command breaking for a 4-3 lead and holding her serve from 0-40 in the next game.

"That was the key," said Navratilova, who served and volleyed ferociously. "I went in on my second serve the only time at 0-40, and it worked. I got on the top."

Navratilova has slimmed down and settled down emotionally since her tearful first round exit at the hands of Janet Newberry last year. Ironically, she also considers the WTT trade for Turnbull a turning point for her because Boston coach Roy Emerson helped calm her down and channel her considerable talents.

Barazzutti, a tough, experienced, industrious clay court player who had never been past the second round here, won eight straight games from 1-2 in the first set and never looked back. He has lost only 22 games in beating Bill Scanlon, Ilie Nastase, Mark Edmondson, Butch Watts and Gottfried in straight sets.

Gottfried, winner of four tournaments this year and No. 2 man in the Grand Prix standings, had one of his worst days. He hit some wild forehand volleys and never had any consistency to his ground game.

As Barazzutti kept whacking his steady groundstokes, passing repeatedly off the backhand, Gottfried became increasingly frustrated and confused. He didn't know when to attack and when to stay back and rally. He came in on bad approach shots, paid for the indiscretion and quickly unraveled.

"I think Gottfried don't play very well today," said Barazzutti, the son of a poor truck driver who now makes more than $150,000 a year from prize winnings and endorsements in Italy, where he is ranked No. 2 behind Adriano panatta.

"He came to the net every time on my backhand, and every time I pass him."

It was almost that simple.