The Auburn, Washington native played his high school football at Puyallup High School. At Stanford, he played both guard positions and occasionally lined up as a fullback for the Cardinal in short-yardage situations. He was the 2015 Outland Trophy winner and was a consensus All American. He was drafted in the first round by the San Francisco 49ers along with fellow Morris Trophy winner DeForest Buckner marking the first time ever that winners in the same year were drafted by the same team. Garnett’s father Scott played for the 49ers after playing college football at the University of Washington.