O’Hara, who claimed his first victory in the Tartan Tour event at Moray in resounding fashion in 2017, started the second and final round in this shortened version with a two-shot lead after a bogey-free eight-under-par 64.
But the North Lanarkshire Leisure-attached player found himself trailing by two shots heading to the seventh tee after Doak covered the opening stretch in five-under, having made an eagle-3 at the fourth, as well as picking up birdies at the second, fifth and sixth.
The pair then found themselves sharing the lead when O’Hara birdied the seventh and Doak bogeyed that before another two-shot swing went in O’Hara’s favour as the same thing happened at the ninth.
O’Hara then mixed three birdies with two bogeys on the back nine as he carded a 68 to land the £3,000 top prize in the Arnold Clark-sponsored event with a 12-under-par total.
Renaissance Club-attached Doak, a two-time winner, signed for a 69 to share second spot with East Renfrewshire’s Gavin Hay and Auchterarder amateur Rory Franssen after they both signed for 68s.
“It was a good tussle with Doaky and it is good to win the big ones,” said O’Hara. “Though it is hard to do it in every single round, I’ve been playing very steady the last month or so, trying to keep everything as simple as possible.
“I was pretty steady again today, hitting it down the pins a lot and holing some nice six and seven-footers.”
O’Hara, who has been the Tartan Tour’s dominant force in recent years, finished in the top 25 in last week’s IFX Championship at Harleyford - the opening event on this season’s PGA EuroPro Tour.
“At one point last week, I thought I was going to win it but, unfortunately, my challenge fizzled out,” he said. “However, if I can get a run of EuroPro Tour events, I am confident I can feature up there.”
Tom Higson (Gleneagles Hotel) and Graham Fox (Clydeway Golf) finished joint-fifth on seven-under, one ahead of a group that included former PGA champion Andrew Oldcorn (Ratho Park).