Meg Mallon, 28, of Ramona, Calif., shot a four-under-par 67 in her final round and vaulted past the leaders of the first three days to win the U.S. Women's Open, at Colonial Country Club.

"No one's more surprised than I am," said Mallon, who only several weeks before had won at the LPGA Championship after being shut out of a major championship in her first four full years as a professional. "I'm patient," she continued, in explaining her development. She was cool too, in spite of the near 100 degree heat that baked the course.

Mallon's total of one-under 283 was two strokes better than that of Pat Bradley, of Camp Hill, Pa., who was the first-round leader with a two-under 69. Bradley then shared the second- and third-round leads with Joan Pitcock, of Fresno, Calik. At even-par 142 and at one-over 214 before Mallon made her move. Bradley shot even-par 71 in her final round while Pitcock slipped to a 75 and finished seventh.

Beth Daniel, of Delray Beach, Fla., posted the lowest round of the Open with a 66 on Sunday and that lifted her into a tie for 11th place. Two former U.S.Girls' Junior champions cracked the top 10: Amy Alcott, at 286, was third, and rookie Brandie Burton, at 290, was tied for eighth. Betsy King, trying to become the first player to win three consecutive Women's Opens, improved dramatically with a final-round 68, but her 294 still was well off the pace and left her tied for 28th.

The medal for low amateur went to Tracy Hanson, of Rathdrum, Idaho, who had won the U.S. Women's Amateur Public Links just three weeks earlier.