In a tough grind the scores were locked three times before a final try to Max Lees off a deft round-the-corner ball from skipper Riley Graham proved the match-winner.

It took a six-point lead on the stroke of the three-quarter-time break, with the Butchers good enough hold the Greyhounds off in the final term.

"I honestly didn't l know what I was doing, I just ran down that edge, I was lucky enough they fell for the first dummy and then it was a bit of a Hail Mary and it paid off," Graham said.

"They were really physical, we knew they'd come at us hard, they're a big side it's how they play. We knew if we could stick with them early we'd roll over them at the end and that's what we did.

"We really ground out the win and that's what we've done all year. We trained hard all through preseason, this team's had a really good work ethic and I think the fitness told in the end there.

"It's massive for us, it's what we worked for all year and we don't expect anything less at this club."

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In a back and forth affair, Lees try was the final blow, with Avondale unable to crack the scoreboard again after levelling up at 18-all with 20 minutes to play. They pushed hard for a leveller down the stretch but Kyle Trebel had the final say with a penalty goal that put the game out of reach inside the final minute.

The Open Age title is the first time the Butchers have claimed the top prize on offer in Illawarra League since 2014, with coach Aaron Beath full of praise for his young side.

"We were pretty confident coming in, we finished number one [on the ladder] for a reason and we knew if we brought that game we'd go close to winning it," Beath said.

"It wasn't our best performance but the boys hung in there, we've had the same group all year and they've worked really hard for one another.

"They really deserved it. We probably gave away 10-15 kilos per man so we knew we had to play smart. The stop start footy probably suited them a bit but the boys kept turning up.

"They were attacking our line for that last 15 minutes and the boys kept getting off the line, doing those one per-centers we always talk about and got a result they've deserved all year. No one can take it away from them."

Kenny Ahoevelo was outstanding for the Greyhounds and grabbed the first try, but the Butchers hit back with halfback and man of the match Mitch Francis scoring a try and laying on another for Graham.

The Greyhounds hit back through five-eighth Bryce Hoskins, though Francis grabbed his second from long range against the run of play for an 18-12 lead at the break.

Avondale struck first after the break through fullback Jamin Williams to level the score at 18-all but it proved their final points, with Lees' dagger and Trebel's goal sealing the deal.

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Greyhounds coach AJ Martin Peterson said he couldn't have asked anymore of his side, but conceded they didn't show enough composure down the stretch.

"We had a few blokes come off injured, losing [starting prop] Jeco Makatoa in the first set set us back a lot," Martin Perterson said.

"I think the emotion might have got to them there in that last quarter but Thirroul were just a great side, they played 80-minute footy and took all their chances. Hat's off to them, they're a really good side.

"We didn't get the result but I'm proud of the boys, they dug deep for me all season. Some games you win, some you don't, we didn't win today but we're still brothers and we'll go enjoy Mad Monday."

It was a step up in grade for the Greyhounds, who fielded Open Age and second division sides this season, and Martin Peterson said a fair chunk will look to return and go one better next year.

"We really built a good brotherhood here, I want to thank Illawarra [Rugby League] for bringing us into the competition this season, I've loved it," he said.

"It was such a good year, it was awesome to see the locals get around us even though not all of us were from down here. When we came together, from the first session, it just clicked.

"There's 10-12 of us who want to stay around, a couple of the local boys from down the coast want to come up and play and there's some good local young boys in third division that want to push up so hopefully we'll be back."

In other results at Ziems Park, Wests proved too good for Dapto in the under 18s decider, winning 42-20, while Figtree celebrated a premiership in its return season with a 28-22 win over Wests in the second division grand final.