The 43-year-old John spent the past four years at Arizona after spending one season as assistant under Ernie Kent at Oregon. He also was an assistant at Butler for eight years and was thought to be a finalist for the Bulldogs' last two coaching vacancies.
South Florida coach Seth Greenberg and University of the Pacific coach Bob Thomason also interviewed for the position.
"This is a guy who's paid his dues," said OSU AD Mitch Barnhart said. "He's worked on his craft to where he's at the point where he should have his own program and have some fun. People sometimes get caught up in the glitz and glamour, and we lose track of the people who have a great work ethic and have given unbelievable effort."
John received praise from two of his former bosses.
"Jay is very good with people," Kent said. "He is the type of guy that will work with passion.
"I think the situation at Oregon State is a great opportunity for Jay," Lute Olson said. "He knows a lot of the players in the program. We had been involved in trying to recruit Philip Ricci, Brian Jackson and Jimmie Haywood."