Graham and Ciaran Paterson (Royal Burgess) shared the lead on four-under-par after the opening two rounds over the Swailend course at the Aberdeenshire course on Saturday.
Graham, the younger brother of 2020 Stephen Gallacher Foundation Trophy winner Gregor, followed an opening 71 with a 69 while Paterson signed for scores of 73-67.
On a day when all the competitors found the Hawkshill course a tougher proposition, the pair were still locked together after carding matching 76s in the final circuit.
That meant a sudden-death play-off, which was won by Graham at the first extra hole with a par after Paterson had strayed out of bounds on the right.
Next up for Graham is a chance to match his brother’s feat in the Stephen Gallacher Foundation Trophy at Castle Park.
Forfar’s Robyn Fowlie won the Paul Lawrie Junior Quaich, the girls’ event, by three shots, having set up her victory with an opening 74.