Those roles were reversed in Celtic's recent 3-0 win over Kilmarnock as the pair vie for a place in Tony Mowbray's midfield.
The younger McGinn followed McCourt from Derry City to Parkhead earlier this year and both struggled to make inroads on the first team last term.
But Mowbray has given both of them several opportunities and told them fellow wingers Aiden McGeady and Shaun Maloney are not automatic choices.
So McCourt believes he and his countryman can both carve out successful careers.
"I am 100% competing with him because we both play in the same position and we both came over from Derry," McCourt said.
"But we have got a great relationship, we are great friends off the park.
"When we go away with Celtic, we room together, and when we go away with Northern Ireland, we room together.
"So it's a friendly rivalry and we both push each other on.
"I just hope we both make a great career for ourselves, both with Celtic and Northern Ireland."
The 25-year-old added: "There are four of us, there's Aiden and Shaun as well.
"The manager said whoever is going to be on form out the four of us will play.
"It's definitely not just between me and Niall, there are four wide men and whoever is on form will get the nod."
McCourt made his international debut against Spain in 2002 as a teenager while playing for Rochdale, but won only his third cap against Serbia.
"It was nice to be back in the squad and I got a run-out this time so it was good," said McCourt.
"Serbia were a good side, they finished top of France's [World Cup qualifying] group. So it was a good experience for us and just nice to get a run-out again."
But McCourt is hopeful there will be many more caps to come as he continues to develop under Mowbray.
"I'm enjoying it, playing a lot more than I was last year," he said. "I think playing first-team football helps.
"I'm playing with better players. It's the first time in my career I've played with this standard of player, other than the odd international game.
"When you're working with good players day in, day out, it definitely helps."
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