The issue wasn't long in doubt on Sunday. UCLA pounded out 10 hits in the first five innings to take an 8-1 lead.
Andres Alvarez had three of the Cougs' six hits.
Washington State plays Gonzaga in Spokane on Tuesday at 6 p.m. (no TV).
WSU then faces the No. 1 team in the nation in the second-to-last series of the regular season, starting a three-game series at Oregon State on Friday.
All three WSU-OSU games will be televised on the Pac-12 network.
WSU finishes up the regular season at home against No. 10 Stanford May 25-27.