Scotland 181 for 4 (Coetzer 74, Munsey 50) beat Ireland 180 for 7 (O'Brien 65, Stirling 56) by six wickets
Paul Stirling and Kevin O'Brien each notched half-centuries as part of a 115-run opening stand, an Ireland T20I record for any wicket. But left-arm spinner Mark Watt nabbed both sandwiched around No. 3 Andy Balbirnie in a game-changing spell of left-arm spin to restrict Ireland to a well-under par 180 before Kyle Coetzer and George Munsey produced a Scotland T20I record opening stand of 109 in a six-wicket win.
After a morning display in which Oman scored 120 off their last 10 overs after being sent in, Ireland appeared destined for 200 or more given the platform that was laid by Stirling and O'Brien. But the innings stuttered after Watt intervened, paired with some sharp catching on the boundary by Michael Leask and Munsey. O'Brien drove to Leask at long-off before Balbirnie skied a sweep to Munsey at deep square leg. Leask made his presence felt again at long-off to nab Stirling as Ireland lost 3 for 15 to slip to 130 for 3.
Richie Berrington was an unsung hero on the day, returning 0 for 26 in a spell that built on Watt's breakthroughs to put the brakes on Ireland's batting once the top order was removed. Safyaan Sharif was then responsible for two wickets in the 17th, knocking back Lorcan Tucker's off-stump before running out Simi Singh with an underhand flick in his follow-through on the next ball to make it 138 for 5.
Ireland fought back in the final three overs as Alasdair Evans' short-ball plan failed to the tune of 35 runs conceded off the 18th and 20th. George Dockrell's cameo of 15 not out off 7 balls propped up the total but Ireland's lull in the middle of the innings came back to bite them, as did an uncharacteristically poor fielding display.
Coetzer was named Man of the Match for his 74 off 38 balls to pace the Scotland chase. But he benefitted greatly from three dropped chances - the first on his second ball when he was yet to score - as well as being caught off a no-ball when Peter Chase overstepped with Coetzer driving to Shane Getkate at long-off on 39.
At the other end, there was no doubt about the crispness of Munsey's knock. He scored Scotland's first 18 runs across the opening two overs of the chase, driving Singh back down the ground for four and six. He brought up his half-century off 26 balls, two slower than Coetzer, before a false drive against Getkate resulted in an edge behind to Stuart Poynter in the ninth.
Coetzer smashed back-to-back sixes over long-on in the same over to bring up his fifty, then followed it with two drives through mid-off against Boyd Rankin in the following over for another pair of boundaries. He took one more off Rankin through mid-off again in the 13th before he was beaten driving on the next ball to fall for 74, the seventh half-century of the day on the pitch.
By that stage, the required run-rate had come down to less than a run a ball. Despite Berrington and Matthew Cross both falling for ducks to complete a mini-collapse of 3 for 3, Calum MacLeod and Craig Wallace added an unbeaten 37 together to see Scotland home. MacLeod ended the match with a straight six off Peter Chase to clinch victory with nine balls to spare.
For Scotland, it's their second ever T20I victory over a Full Member following a win over Bangladesh at the Hague in 2012. It also kept them alive for a shot at the T20I Quadrangular Series title. A win over Oman on Sunday would take them to 2-1. Ireland also has a chance to end with the crown if they can beat 2-0 Netherlands on Sunday, which would create a three-way tie to bring the net-run-rate tiebreaker into play.
Peter Della Penna is ESPNcricinfo's USA correspondent @PeterDellaPenna