Harvard's tennis team scored a major upset Saturday when it stunned mighty Pennsylvania 5-4. Penn had been picked with Princeton as a pre-season favorite to win the Eastern title.

The victory, which extended Harvard's unbeaten string to four matches, was in doubt until the final match of the afternoon. Jose Gonzales and Kent Parrot clinched the triumph with a convincing 6-2, 6-2 win at number two doubles.

Several Crimson racketmen shared in the heroics. Parrot, Rocky Jarvis, and Terry Oxford each captured important singles contests. Jarvis and John Levin added a clutch doubles victory.

Oxford provided the most timely triumph. With Harvard trailing, 3-2, a defeat at number five singles could have spelled disaster. But the Crimson junior refused to fold. He revitalized Harvard's challenge with a sensational three-set win over Penn's diminutive pusher, Richie Cohen.

Cohen uses a ping-pong style which includes soft, base-line Jobs and tricky underhand serves. Oxford showed exceptional patience throughout the match. When his overhead finally found its range, he overwhelmed Cohen and pulled out a 6-8, 6-3, 6-2 win.

After Oxford's victory, Harvard still had to capture two doubles matches. Levin and Jarvis provided the first win by defeating Hugh Curry and Bill Powell, Penn's number one combination, 6-3, 6-2.

Levin and Jarvis played nearly flawless tennis against their highly-rated opponents. By the end of the match, Curry and Powell had become frustrated to the point of disbelief. The lopsided win helped to assuage Levin's singles loss to Curry.

Jarvis and Parrot each won two matches for Harvard. Jarvis demonstrated pinpoint accuracy in topping Penn's Fred Levin at number two singles, 6-4, 6-3.

Parrot surprised everyone with his quick 6-1, 6-4 triumph over Powell. Since returning from his honeymoon last week, Parrot has produced two outstanding efforts at the fourth singles spot. He and Gonzales have also formed a solid doubles combination. Against Penn, they crushed their opposition to win the deciding match.

Larry Terrell made his second start of the season at number six singles and lost a heartbreaker, 4-6, 6-1, 8-6. Terrell led 5-4 in the third set but was unable to break service. The squash star experienced a rough afternoon as he and Rick Sterne also lost at third doubles, 6-3, 6-2.

Harvard journeys to Cornell and Williams Wednesday and Friday and then will face Princeton here Saturday in the ECAC's most crucial match of the year.