Liz Brenner led three players in double figures with 15 kills Wednesday night as Oregon swept Washington State 25-22, 25-22, 25-19 in Pac-12 play at Pullman.
Ariana Williams and Martenne Bettendorf combined for 23 kills for the Ducks (18-11, 11-8), who took over fourth place alone after California lost to Arizona State.
Jaicee Harris had nine kills for the 11th-place Cougars (18-14, 5-14).
Camryn Irwin added 27 assists and Kate Sommer had 13 digs for WSU.
The middle game was tied 14 times, the final time at 19, until Brenner had two kills during a 3-0 Oregon run.
Oregon and WSU only meet once in conference play.
The conference season ends Friday with WSU at Washington.
(5) Washington 3, Oregon State 1: Krista Vansant had 15 kills and 11 digs and Kaleigh Nelson added 13 kills and four blocks as the fifth-ranked Huskies (25-2, 17-2 Pac-12) clinched at least a share of the conference title by defeating the Beavers (9-21, 0-19) in Seattle.
The Huskies remained one game ahead of Stanford (16-3 Pac-12), which swept Arizona.