The Star first linked Onen with the Owls earlier in the year, and he later came in for a trial spell at Middlewood Road – playing and assisting in an U23 game in September.
Now, after Darren Moore has had time to mull things over, it has been announced that the former Arsenal youngster has put pen to paper on a deal in S6.
Speaking to the club’s official website after putting pen to paper, Onen said, “I’m delighted to get it all signed and sorted and my main focus is to get as fit as I can.
“I got a little taste of first team football last season with Reading and made my debut against Norwich - it’s made me hungry for more. I know what I need to do and where I want to be.
“I had a good week training here, spent time with the first team and the lads were very welcoming and now I just want to push on.
“I played in the game at Coventry and I thought we played really well that day, there were a lot of young lads from the club playing but they did well and now I can’t wait to get started.”
He’s expected to start life with the U23s as he gets himself back up to speed, and will team up with Lee Bullen’s side when they face Hull City on Wednesday.