The 20-year old is a versitile midfielder, just what Brian Little has been searching for, and will provide ample cover for the injured Jason McAteer and Danny Harrison over the next month according to boss Brian Little.
Last year, Steven made his debut for Luton Town and went on to make a further 19 appearences, playing a big roll in their Championship winning campaign.
O'Leary goes straight into the squad for tomorrow's home match against Colchester and will wear the number 19 shirt.