Ragin, out of Wilsonville High School, has transferred from California where he appeared in eight games last season.
The former Rivals.com three-star recruit originally chose Cal over Oregon and Oregon State when coming out of high school after recording 99 tackles and 15 sacks as a senior.
Oregon also added junior college transfer cornerback Dominique Harrison, a three-star recruit who is part of UO's 2014 recruiting class.
The other early addition is freshman wide receiver Jalen Brown, a four-star recruit out of Phoenix, Ariz.
Ragin will likely have to sit out the 2014 season. Harrison can compete right away to replace departing cornerback Terrance Mitchell, who has entered the NFL Draft. Brown joins a litany of wide receivers battling to replace senior Josh Huff.