The former Aberdeen ace would prove to be the match winner as he was introduced from the bench with devastating effect as his strike found its way past Nathan Gartside on 75 minutes.
The visitors will feel they should have at least walked away with a share of the spoils for their efforts as in-form striker Ben Wilson went close on numerous occasions to finding the back of the net.
However, the success moves the Glens up to third in the Premiership table and McGinn insists he has to be patient for his chance after being dropped for recent outings.
He said on Glentoran's media channel: "I think it was a fair result on the balance of play.
"Credit to Cliftonville, they came here and tried to play football on a sticky pitch.
"They created chances and you always know they will regardless if they're ahead or behind.
"We knew one goal was probably going to win the game and thankfully I came on, made an impact and scored.
"That's me up and running for the season and I'm delighted.
"Any season I try and score as quick as I can and it was great to come on and score the winner.
"Daire crossed the ball and overhit it, Singo (James Singleton) has gone to head it and I've just reacted to their defender missing it.
"I went towards Casey, I knew he was on a yellow so wanted to get at him, done a shimmy and cut inside.
"I was delighted to see the ball hit the back of the net as it's been a frustrating couple of weeks as I haven't been playing.
"Being who I am, I'll always keep my head down and keep working hard and try to help the team in any way I can."
The experienced McGinn admits he enjoys passing on his knowledge to younger members of the squad and that the signing of Fuad Sule has helped the Glens pick up several narrow victories this season.
"It's great being able to do that," he added.
"I was in their shoes many moons ago playing in the Irish League.
"To see the likes of Leon Boyd coming on and there's other biting at the bit to play.
"Looking back a couple of weeks ago, the squad looked a little bit small but you can see now that four or five lads are being left out of the squad.
"It's a competitive edge you need at a big club like Glentoran.
"I think it's a more street-wise squad than last year.
"Fuad Sule has obviously been a big help in midfield, having Paddy McClean back, we have players in the squad who are organised.
"We probably didn't play our greatest, we've grinded out results against Glenavon, Loughgall and now today, so it shows if we keep clean sheets we will always have chances to win games."