Hasay, a junior from Arroyo Grande, Calif., won in 4:22.16, to defeat Canada's Annie Leblanc, who ran 4:24.97. Leblanc will be joining the Ducks this fall as a freshman.
In other international competition, freshmen Allie Woodward and Ryan Pickering are in Barcelona, Spain, for the IAAF World Junior Track and Field Championships.
Woodward will cap an impressive freshman season in the 5,000 meters on Wednesday. The Green Bay, Wis., native placed fifth in the 10,000 meters at the NCAA Championships and was third in the 10,000 and sixth in the 5,000 at the inaugural Pac-12 Championships.
She won the U.S. junior title in the 5,000 meters last month in Bloomington, Ind., in a personal-best 16:15.27 to qualify for Barcelona.
Pickering, who redshirted the 2012 outdoor season, will be in the men's 10,000 meters on Tuesday night. The freshman from West Palm Beach, Fla., was the American junior champion in the 10,000, winning the title last month in 30:56.77.