Sophomore quarterback Tom Tunnicliffe passed for 293 yards and the winning touchdown today as Arizona upset top-ranked Southern California, 13-10, in a Pacific-10 Conference game.

Tunnicliffe, from Burbank, Calif., completed 21 of 37 passes and consistently confused the Southern Cal secondary with varying pass patterns while being given excellent protection by his offensive line.

Arizona gained 405 yards to just 297 for Southern Cal, which had been averaging 483 a game. Trojan tailback Marcus Allen gained 211 yards, going over 200 for the fifth consecutive game to tie the NCAA record set by Cornell's Ed Marinaro in 1971.

It was the first loss in five games for Southern Cal, which has one Pac-10 victory. Arizona is 3-2 overall, 2-2 in the Pac-10. Arizona had not beaten Southern Cal in 11 football games between the schools.

The winning touchdown came with two seconds left in the third quarter when Tunnicliffe threw Vance Johnson a short pass at the Southern Cal 10 and the tailback sprinted into the end zone.

That drive began after the Trojans' Fred Crutcher fumbled at the Arizona 41. The third Southern Cal fumble of the game was recovered by Jerome Crimes.

Tunnicliffe then engineered a quick drive highlighted by a 25-yard pass to Brad Anderson, who made a spectacular sideline catch at the Southern Cal 15.

Two plays later, Tunnicliffe passed to Johnson.

Southern Cal got off to a quick start. On its second possession, Allen raced 74 yards down the middle of the field for a touchdown. The Trojans made it 10-0 with 7:32 played on Steve Jordan's 41-yard field goal, but the Arizona defense then shut down the nation's second-leading offense and the Wildcat offense began pecking away.

Arizona made it 10-3 with 30 seconds left in the first half on Brett Weber's 47-yard field goal and made it 10-6 with 5:40 left in the third quarter on Weber's 25-yard field goal.

Tunnicliffe threw to eight receivers during the game, with Kevin Ward catching three passes for 69 yards. Bob Carter and Anderson each caught three for 66 yards and Mark Keel caught four for 53 yards.

It was the second upset in a row engineered by the 6-foot, 185-pound Tunnicliffe, who guided the Wildcats to a 17-13 triumph over Stanford a week ago. He started six games as a freshman, but was No. 2 this season behind junior Mark Fulcher until the Stanford game.

Southern Cal quarterback John Mazur completed only six of 14 passes for 60 yards. Allen, who carried the ball 26 times, also moved ahead of O.J. Simpson into the No. 4 spot on Southern Cal's career rushing list. Allen has 3,520 yards in 668 carries; Simpson had 3,423 yards in 674 carries.

"That was one of the worst offensive performances I've ever seen as a coach," said Southern Cal's John Robinson. "We were beaten by a club that played better football in every phase of the game. Perhaps we underestimated Arizona. They outplayed us and out coached us.

"What surprised me was the inefficiency of our offense to move the ball. We turned the ball over four times. We kept killing ourselves. We learned today that we're not good enough to play without emotion and still win."