The 32-year-old has agreed a contract until the end of the season after his deal at Elland Road was cancelled by mutual consent.
"I'm delighted to bring Jason to the club, it's a deal I've been trying to do for the last two or three days," said Os boss Russell Slade, who also managed the player at Grimsby.
"He's versatile and can play anywhere across the back or in midfield. He's a good utility player with a great attitude and good energy."
Source: PA