The former national junior college player of the year will redshirt one year before becoming eligible to compete with the Tigers in 2018-19.
The native of England, in primarily a reserve role, helped the Ducks advance to the 2017 Final Four.
Bigby-Williams played in 37 games with Oregon, averaging 3.0 points and 2.8 rebounds. He also blocked 28 shots.
Before joining Oregon, he played at Gillette College in Wyoming, where he averaged 16.8 points, 13.6 rebounds and 5.6 blocks his sophomore season.