O'Driscoll took over at Ashton Gate this week, less than a month after his acrimonious departure from Nottingham Forest, and for 65 minutes watched his new charges hold their own against a Leeds side who were barracked by their own fans for an anaemic performance in front of goal.
McCormack's second strike of the week changed the mood, though, putting Leeds on their way to a sixth successive home league win.
They remain in touching distance of the promotion hopefuls and manager Neil Warnock will now look to new owners GFH Capital to provide him with what he needs to try and close the gap.
For O'Driscoll, this was his second encounter with Leeds in just 24 days. He engineered a 4-2 win for Nottingham Forest on Boxing Day and was sacked in the wake of it, and his new team started as though they were keen to rack up a big score too.
Former Leeds midfielder Neil Kilkenny caused havoc in United's box with a chipped free-kick and Liam Fontaine looked to have got in on goal until Sam Byram scrambled the ball away.
With Kilkenny pinpoint in his distribution they were able to get at Leeds and had Cole Skuse had better accuracy when shooting from the edge of the box they would have gone ahead.
It took some brilliance from Paddy Kenny to keep his side in it immediately after half-time, throwing himself to his left at the last second as Byram sliced Richard Foster's cross toward his own goal.
Leeds finally carved a decent chance and with it a goal. Loan midfielder Ross Barkley had been their biggest spark all afternoon and when he stood up a 65th-minute cross, McCormack made sure he got above Foster to plant a header past Tom Heaton.
There had been little to shout about before the goal and the game quickly reverted back to type, with neither side doing little to prove that the goal was anything other than a one-off moment of excellence.