Having crucially saved his par on the 14th with a 20-footer from off the green, Fox made birdie on the 15th to stay right in the thick of it.
With O’Hara spilling shots at 10 and 13, there was nothing between the sparring duo as they came down the last but Fox delivered a knock-out blow with that thrilling putt for a title-winning three.
“I lucked out on the back-nine,” added Fox with a wry chuckle. “Paul got a bit unlucky with a couple of his shots and I holed a couple of monster putts. It was just momentum. And a bit of luck. You need that on days like this.”
O’Hara signed off with a 71 for a one-under tally of 141 while local man Albert MacKenzie and Aberdeen veteran Scott Henderson, the Northern Open winner back in 1996, shared third on 145s.
Strathlene’s Ryan Bain took home the Bookless Cup as the leading amateur after finishing in a share of ninth on five-over.