Tyson, who helped to steer Oldham to promotion in 201, left the club at the end of that season..
“It was an easy decision . . . just like going home,” said 23-year-old Tyson, who was one year into a three-year full-time contract at Sheffield Eagles when it emerged they were facing a financial crisis and would be going part-time again next year.
Oldham chairman Chris Hamilton said: “We are delighted he has chosen to come back to us.
“We know our fans will be too. He was definitely a fans’ favourite. He excites them with his all-action, no-nonsense displays on attack and defence.”
Head coach Scott Naylor: “This is a brilliant signing. He was outstanding when we won promotion.
“We tried everything to keep hold of him and Adam (Neal) but they wanted full-time rugby and we could understand that.
“Bringing them both back underlines our ambition as a club and our desire to keep moving forward in the Championship.
“George will be a better player than when he left us and I’m looking forward to working with him again and to re-familiarising myself with the banter he brings to the dressing room and with the passion and aggression he takes on to the pitch.”
Equally at home at centre or second-row, Tyson graduated from reserves to first team in 2014 when, as a 20-year-old, he played in 16 League 1 games – 14 of them off the bench.
In the next season, he scored 13 tries in 23 senior games as Roughyeds moved up to Championship status and he was nominated for League 1 player of the year alongside his then club captain Lewis Palfrey, who won it.
Tyson said: “I enjoyed my time at Sheffield, but due to the club’s unfortunate circumstances a return to Oldham was the right move.
“There are a lot of familiar faces here, including Scott, ‘Spanner’ (Lee Spencer) and Pete Carey (the three coaches). Peter coached me at Salford as an under-16 and an under-18 so it will be like home from home.
“I’ve a load of friends at Oldham and I’m getting a job outside rugby so everything is working out fine.
“I’m looking forward to putting on the Oldham shirt again.”