The school made the announcement as part of the release of a complete depth chart Friday.
Adams was a late arrival to Oregon's training camp as he finished up his undergraduate requirements, and he beat out junior Jeff Lockie, Marcus Mariota's backup the past two years, to win the job.
"The separation was enough that as we began today we kind of started our true game week preparations, so the timing worked out for everything," coach Mark Helfrich said Saturday of making the decision to anoint Adams.
In three years at Eastern Washington, Adams threw for 10,438 yards, 110 touchdowns and 31 interceptions. He was twice named the runner-up for the Walter Payton Award, given to the FCS player of the year. Adams has been off-limits to the media since officially joining the team Aug. 13 and is not expected to speak publicly until after the Ducks' first game.
In two seasons as Mariota's backup, Lockie threw for 264 yards, one touchdown and one interception in 19 appearances. Despite Adams' much-anticipated arrival, Lockie was expected by many to start the opener due to his more advanced understanding of the Ducks' offense and the minimal time Adams has spent with the team.
ESPN's Chantel Jennings contributed to this report.