The Ducks were announced as the conference favorites Friday before Pac-12 media day.
Oregon received 14 of the 25 first-place votes in the poll, earning 139 points. The defending Rose Bowl champion Cardinal received 11 first-place votes and 134 points.
The two-time division champion Bruins got 12 first-place votes and 130 points in the South polling, edging Arizona State's nine first-place votes and 124 points. Southern California, last year's preseason No. 1, got four first-place votes and 113 points in third place.
Oregon State was third in the North balloting, followed by Washington, California and Washington State.
Arizona was picked fourth in the South, followed by Utah and Colorado.