O'Leary claimed Leeds fans would give him a warm welcome despite his sacking 18 months ago, and he was right, receiving an ovation as he walked to the dugout.
But what followed was a poor advertisement for Premiership football between two sides in serious danger of the drop.
With a torn hamstring ruling out Lucas Radebe for two months, Leeds caretaker-manager Eddie Gray gave 19-year-old central defender Matthew Kilgallon his first start and the youngster responded with a promising performance, though two late mistakes by the York-born defender went unpunished.
Villa were unchanged, O'Leary deciding to keep Darius Vassell on the bench as Stefan Moore partnered Juan Pablo Angel in attack.
James Milner should have fired Leeds ahead on the half hour when goalkeeper Paul Robinson's long clearance sent the teenager racing into Villa's penalty box, but he swung his boot at fresh air with the net beckoning.
Five minutes later Villa thought they had scored when Lee Hendrie's free-kick from the right brushed off Angel into the net. Referee Steve Bennett at first signalled a goal, but then spotted a linesman's flag raised for handball against Angel and the goal was disallowed.
It was Leeds' turn to have a goal ruled out ten minutes into the second half when Milner's free-kick from the left was touched in at the far post by Michael Duberry, but the offside flag was raised.
Jermaine Pennant's pace and trickery caused problems for Villa left-back Jlloyd Samuel until the hard-working Gareth Barry gave his team-mate extra protection and Pennant's early threat fizzled out.
Eirik Bakke left the Leeds bench in the 64th minute for his first appearance since knee surgery in the summer, skipper Dominic Matteo giving way, and Aaron Lennon later replaced Pennant.
Villa, meanwhile, replaced Moore with Thomas Hitzlsperger, and Hendrie with Vassell, but the game petered out into a tame goalless draw.