Langston Morris-Walker made a go-ahead layup with 26 seconds left, lifting
Arizona's T.J. McConnell missed an off-balance shot with 1 second left, and Oregon State fans rushed the court at Gill Coliseum.
Morris-Walker had 12 points and eight rebounds, and Gary Payton II had 10 points and nine rebounds for the Beavers (11-4, 2-1 Pac-12).
McConnell had 13 points and six assists, and Rondae Hollis-Jefferson scored 14 points for the Wildcats (14-2, 2-1), the third top-ranked team to lose Sunday. No. 2 Duke lost to N.C. State and fourth-ranked Wisconsin was defeated by Rutgers.
A gritty, defensive matchup, there were 20 lead changes and 15 ties. Neither team held more than a four-point lead.
The Beavers took a 56-52 lead with 1:33 left after Malcolm Duvivier was fouled on layin and made the free throw for a three-point play. Gabe York responded for the Wildcats with a three-pointer with 1:07 remaining.
Duvivier missed another layin, and Oregon State fouled Hollis-Jefferson on the rebound. He made one of two to tie it at 56-all.
Payton came into the game leading Oregon State with 12.4 points, 8.1 rebounds and 2.9 steals per game. The junior college transfer is the son of former Beavers All-American and NBA star Gary Payton.