Stewart caught 38 passes for 514 yards and four touchdowns as a sophomore this past season. He has two years of eligibility remaining.
The 2022 five-star recruit from Memphis, Tennessee, played in 10 games for the Aggies as a freshman, starting eight. He had 53 receptions for 649 yards and two touchdowns to earn SEC All-Freshman honors.
He's one of 19 scholarship players who have entered the transfer portal from Texas A&M since November.
Stewart is joining an Oregon team that has been active in the transfer portal, adding former Oklahoma quarterback Dillon Gabriel and ex-UCLA quarterback Dante Moore to help replace outgoing signal-caller Bo Nix.
Stewart will help replace leading receiver Troy Franklin, who has declared for the NFL draft. Tez Johnson, Oregon's second-leading receiver, is returning, as is Traeshon Holden. They combined for 16 receiving touchdowns this past season.