Oregon soccer (7-5-1, 1-4-0 Pac-12) traveled to Boulder, Colorado, to face the 16th ranked Buffaloes (11-0-3) on Saturday.
The match was the third of five straight grueling matches against 2017 NCAA tournament teams for the Ducks.
The Buffs dominated the first half, getting out to a 3-0 lead with two goals coming off penalty kicks from junior midfielder Taylor Korniek, and the third off a high-flying header from sophomore forward Marty Puketapu.
The Buffs maintained this lead and took home the victory 4-1, remaining undefeated and tying the longest unbeaten streak in program history at 12-0-3.
The loss is the fifth in a row for the Ducks, who fall to 7-6-1 on the season after reaching an all-time high NCAA ranking of 14th in September.
A handball by the Ducks provided the first penalty kick opportunity for Korniek, who tucked the ball into the bottom left-hand corner past Oregon redshirt senior goalie Halla Hinriksdottir.
Puketaku, the sophomore forward from New Zealand, headed in the second goal for the Buffs off an assist from redshirt junior forward Stephanie Zuniga, and after Korniek’s second penalty kick, the Buffs had stretched a formidable lead.
Oregon sophomore midfielder Chardonnay Curran provided the Ducks their only goal of the match in the 60th minute off a sprinting header on the right side of the box into the bottom right-hand corner of the goal.
The Buffs responded with a soaring lob from Chaynee Kingsbury to a diving header from redshirt freshman Libby Geraghty, who sealed the game with her first career goal.
The loss is a tough start to three straight road games for the Ducks, who now travel to Los Angeles to face No. 10 UCLA and No. 2 USC.
Follow Bryce Dole on Twitter @DoleBryce