Goodwin had only officially been installed as Dons gaffer on Friday night following the sacking of Stephen Glass, fired in the wake of Aberdeen’s meek display in losing 2-1 in a Scottish Cup fifth round tie against the same opponents at the same ground a week earlier.
And things looked good for the former St Mirren boss when Vicente Besuijen put Aberdeen 1-0 up after 34 minutes by tapping the ball into an empty net after taking a square pass from Adam Montgomery.
But Motherwell – who were the better team overall – were rewarded for their second half pressure after 68 minutes when O’Hara shot home a rebound after Kevin van Veen’s initial attempt had been parried by away keeper Joe Lewis.
Aberdeen, not coping well with the injury-enforced absence of influential captain Scott Brown, were under the cosh in the first half with O’Hara testing Lewis with a shot after winning the ball near the visitors' box.
Van Veen – a scorer of four goals in three wins over Aberdeen earlier in the season – was a constant menace once more and forced a good save from Lewis after running onto an O’Hara through pass.
Van Veen was then unlucky when he charged down a Lewis clearance but the ball hit the side netting.
The Dutch forward then came agonisingly close to breaking the deadlock when he sent a 20-yard free-kick against the inside of the post after a foul had been awarded for Jonny Hayes’ challenge on O’Hara, an incident which led to Bevis Mugabi squaring up with ex-’Well defender Declan Gallagher.
The Dons hit back and Lewis Ferguson, twice, and Calvin Ramsay forced home keeper Liam Kelly into saves.
The visitors’ Connor Barron then floated a fine ball to Christian Ramirez, who netted, but the ‘goal’ was disallowed for offside.
After Besuijen’s opener and O’Hara’s leveller, the Steelmen could have won it at the death but Connor Shields lofted a fantastic chance over the bar in injury time.