Scotstown and Gweedore will meet in the Ulster Club Football Final in two weeks after earning contrasting victories in Sunday's semi-finals at Omagh.
The Monaghan champions hit four late points - including a controversial winning free - to edge out Coleraine 1-14 to 2-10 in the first game.
Three first-half goals from Dara O Baoill then helped Gweedore surprise Crossmaglen 4-11 to 0-16.
Veteran Kevin Cassidy starred for Gweedore as he hit their fourth goal.
The two semi-finals were watched by a crowd of 7,794 as the Ulster Council's decision to stage a double header at Healy Park was vindicated
Crossmaglen finish with 13 players
Crossmaglen finished the game with 13 players after Johnny Hanratty was sent off for the second match in a row immediately after half-time and Rian O'Neill was red carded in injury-time after top-scoring with nine points for the 11-time Ulster champions.
Two Oisin O'Neill points helped Crossmaglen take an early 0-3 to 0-1 lead but O Baoill put Gweedore ahead with his first goal on nine minutes and the Donegal side were never to relinquish their advantage.
Midfielder O Baoill's second goal came four minutes later and he completed his hat-trick from a penalty on 24 minutes after Donegal forward Cian Mulligan was pulled down in the square.
That put Gweedore 3-5 to 0-5 ahead although Crossmaglen rallied to hit four unanswered points before the break.
Crossmaglen needed to maintain that momentum after the break but instead Cassidy's goal on 42 minutes - with Cross by now down to 14 men - effectively finished the contest as he lashed home from close range after the ball had come back up an upright.
Fit-again Odhran MacNiallais starred in open play and from placed balls as he contributed 0-5 while Cassidy rolled back the years in his superb target-man role at full-forward.
Naoise O Baoill unselfish work in Gweedore's attack was also crucial as he created space for colleagues with intelligent runs and neat lay-offs.
The McGee brothers Eamon and Neil were part of a Gweedore team that had impressive performers all over Healy Park.
O'Neill's late dismissal for a tired late tackle was a sad end to his afternoon after he had produced an exhibition of score-taking despite Crossmaglen's struggles all over the field.
Scotstown snatch victory over Coleraine
The opening semi-final at Omagh was a completely different story as Coleraine looked set for a first ever Ulster Club final appearance before Scotstown's remarkable late recovery.
A Ruairi Mooney goal put Coleraine four up early in the second half and Gavin McWilliams missed a further goal chance which surely would have sealed victory.
But Scotstown fought back and keeper Rory Beggan kicked two of their late scores including his winning free.
Conor McCarthy and Ciaran Mullan struck early goals at either end.
McCarthy finished off a typically direct Scotstown move for their eighth-minute goal and while Mullan ran through unopposed to quickly net a reply, the Monaghan champions dominated possession in the opening quarter to move into a 1-4 to 1-1 lead.
However, Scotstown's play became ragged in the second quarter and two points apiece from Declan Mullan and McWilliams helped the Eoghan Rua outfit move into a 1-7 to 1-6 lead by half-time.
Coleraine move four ahead after half-time
Shane Carey levelled for Scotstown after the break but Mooney's goal on 35 minutes restored Coleraine's lead, with Mullan's third point increasing their advantage to four.
After Francis Maguire replied for Scotstown, a pivotal couple of minutes followed as Coleraine lost Derry midfielder Niall Holly to injury and McWilliams then missed his glorious goal chance.
With only Beggan to beat, McWilliams rounded the All-Star keeper but with the goal gaping, sliced his left-foot shot against an upright, with Kieran Hughes' quick score at the other end adding insult to injury.
Mullan fisted his fourth point on 47 minutes to restore a three-point lead for Coleraine but Scotstown hit five of the last six scores, with McCarthy, Ryan O'Toole and Damian McArdle also on target for the Monaghan champions.
Beggan kicked the winning score from 44 metres in the fifth and final minute of injury-time after referee Ciaran Branagan adjudged that Coleraine's Ciaran McGoldrick had fouled a Scotstown's Donal Morgan.
By the letter of the law, it may have been the correct decision although a number of similar challenges had gone unpunished during the contest.
|Ulster Club SFC semi-finals|
|Coleraine (Derry)||2-10||Scotstown (Monaghan)||1-14|
|Gweedore (Donegal)||4-11||Crossmaglen (Armagh)||0-16|