The 22-year-old cost the Toffees just £60,000 when they bought him from Sligo Rovers in January 2009 and his progress since then has seen him establish himself in the first-team squad.
"He deserves it as he's worked really hard since the early days when we brought him in from Ireland," said the Scot.
"Seamus is one of the young boys. He is improving. He came as a right-back and we've used him wide right and he has got his chance to settle in and I feel I can use him in either position whenever needed.
"He's a long way to go to get to Leighton Baines' (who has been a permanent fixture on Everton's left for years) standard at the moment but that's why we've kept him for a long time because we think there's a chance of good improvement in him.
"Hopefully he will continue to improve. You need a good work ethic and Seamus has that and is improving all the time."
On the trawl for players in the lower leagues, Moyes added: "You have to hope (it is worth the gamble) because if they don't come from the leagues below that means they are already at a club academy.
"If you are a player in the Championship, League One or Two or in Ireland you have to hope the scouts are out watching and you can play well enough to get recognised."
Coleman, currently out injured with a hamstring problem which has forced him to miss three matches, is looking forward to celebrating his new deal with a swift return to first-team action.
"It is never nice to miss games through injury," he told evertontv. "I've a little hamstring injury so hopefully I'll be back in the next couple of games."
Source: PA
Source: PA