Paul White had 16 points and Payton Pritchard had 13 points for the Ducks (19-10, 9-7), who overcame a 13-point deficit in the second half and have won four of six.
Deandre Ayton had 28 points and 18 rebounds, one short of season highs in both, and Rawle Alkins had 24 points for the Wildcats (22-7, 12-4), whose lead in the Pac-12 race was cut to one-half game over USC (21-9, 12-5).
Miller and the school agreed he would not coach a day after ESPN reported that he was heard on FBI wiretaps discussing a $100,000 payment to the representative of a sports agent to ensure Ayton enrolled at Arizona.
Trier, who averages 19.6 points a game, was suspended by the NCAA on Thursday after testing positive for a banned substance.
Arizona's Dylan Smith hit a 3-pointer from the deep left wing to tie the game at 83 with 20.1 seconds left in regulation. Smith, starting for Trier, had 11 points.
Pritchard missed a contested layup with three seconds left to force overtime, but he hit a 3-pointer on the Ducks' first possession of overtime for a lead they never lost.
Alkins made a breakaway dunk and was fouled by Kenny Wooten with 1:55 left, but Alkins was given a technical foul for saying something to Wooten after the play.
Brown made two free throws before Alkins completed the three-point play and Oregon led 92-88.
McIntosh's 3-pointer made it 95-88 with 1:07 left.
Alkins banked in a 3-pointer with 4.0 seconds left as Arizona closed to 96-93 before Brown finished it with two free throws.
The Ducks made 14 of 33 3-point attempts. White had four and Brown, Pritchard and McIntosh had three apiece.
Brown was 6-of-18 shooting from the floor but made 15 of 17 free throws.
Parker Jackson-Cartwright had 15 points for the Wildcats, who had won three in a row and 10 of 12. His layup three minutes into the second half made it 53-40 before Oregon rallied for a split of the season series.
--Field Level Media
Arizona | Oregon | |
DeAndre Ayton 28 | Scoring | Elijah Brown 30 |
Rawle Alkins 5 | Assists | Payton Pritchard 8 |
DeAndre Ayton 18 | Rebounds | MiKyle McIntosh 5 |
DeAndre Ayton 6 | Free Throws Made | Elijah Brown 15 |
Parker Jackson-Cartwright 2 | Steals | MiKyle McIntosh 4 |
DeAndre Ayton 4 | Blocks | Paul White 1 |