A Jake Grace double was the highlight for Forbes as they defeated Dubbo CYMS 26-16 at Apex Oval to win the title.

The Magpies were no strangers to big matches coming into Sunday after winning the 2016 and 2018 Group 11 Grand Finals before but now have made history as the first Peter McDonald Premiership champions.

Magpies coach Cameron Greenhalgh was emotional after the game and knew exactly what led his side to victory.

"We knew we were going to win it with our big defence and that's what won us it today was that defence," he said.

Dubbo CYMS coach Shawn Townsend knows his side saved one of their worst performances of the season for the biggest game of the year.

"I'm pretty disappointed, we didn't play well and got outplayed I suppose," he said.

"We got beaten by what we knew they were going to bring."

Right from the kick off Forbes aimed up and was physical against a mobile Dubbo CYMS forward pack.

It would be Alvin Maungaati who crossed first for Forbes after beating a pair of CYMS defenders out wide to score in the corner to give the Magpies a 4-0 lead early.

But back-to-back penalties from Forbes allowed CYMS easy passage downfield and the Fishies made them pay as Alex Bonham levelled the scores with a try.

Brad Pickering's kick went wide but CYMS started to look like they were in the game.

This continued when Coopa Martin spilled a high ball 10 metres out from his line but CYMS couldn't break through as Mitch Andrews was everywhere in defence.

The game went back-and-forth until Toby Hurford burrowed over out of dummy half to give Forbes back the lead with Nick Greenhalgh nailing the conversion attempt.

A break from Bonham opened up the Forbes defence before Jordi Madden scooped up a quick play the ball only to be tackled by Greenhalgh, a move which the referee deemed a professional foul which led to the Magpies halfback being sin-binned.

However, even with an extra man CYMS could score and thought they had done so through Corey Drew only for the final pass to be ruled forward.

The siren sounded with the score 10-4 in favour of Forbes and both sides were eager to get into the sheds after what was a fiery first 40 minutes.

Greenhalgh returned to the field just a handful of minutes into the second half and immediately made an impact as he set up Grace's first try of the day off a clever short ball.

After Grace's try, the referee deemed CYMS had committed an infringement resulting in an eight-point try opportunity.

Greenhalgh's first attempt was successful and Drew chased the ball in order to save time but in doing so pushed a Forbes trainer out of the way which resulted in him being sin-binned.

With all the chaos unfolding early in the second half, Forbes lead 18-4 with 30 minutes remaining.

Pickering got CYMS back into the match when he picked up a dropped ball to score before converting his own try but Forbes' defence was too good.

The Magpies' middles continued to aim up and were rewarded once again when Grace crossed over for his second try of the match.

The Apex Oval hill erupted as a flock of Magpies fans roared when Greenhalgh's successful conversion moved the score along to 24-10.

CYMS prop Ben Marlin crossed over late for the home side, a try which Pickering once again converted.

But it was too late for the hosts as a late penalty goal on the siren sealed a famous Forbes win.

Forbes snuck into the grand final after a big comeback win over Orange CYMS and their coach believes a lot of people thought they wouldn't be able to match it with Dubbo.

"We were massive underdogs, people didn't rate us," he said.

"We were up and down, we knew in the group that we were right up there.

"If we played our best footy we would be hard to beat."

"To the boys in this side, it doesn't happen every day."

On the other hand, Townsend knows his side just didn't play the way they wanted and felt they lacked discipline at times.

"To win grand finals you've got to be disciplined, you've got to hold the ball," he said.

"We had a bloke in the (sin) bin over something silly, we had a couple of silly penalties at the wrong time and had no composure.

"You get what you deserve there and we were beaten by a better side."

FORBES MAGPIES 26 (Jake Grace 2, Toby Hurford, Alvin Maungaati tries; Nick Greenhalgh 3 conversions, 2 penalty goals) defeated DUBBO CYMS 16 (Ben Marlin, Brad Pickering, Alex Bonham tries; Pickering 2 conversions)