McCoist substituted Honduran internationalist Peralta in the second half of the Ramsdens Cup clash with Queen of the South on Tuesday night.
The midfielder had picked up a yellow card in the first half of the quarter-final showdown and the Gers boss was afraid he would get ordered off.
But the Light Blues gaffer has been pleased with the impact the Central American has made since arriving in Scotland in the summer.
He said: "I'm happy to see him get stuck in. He is 100% competitive, that's the way he plays the game.
"He gets kicked and will be late with one or two tackles himself. That's just the way he plays, there is no malice in him at all.
"I wouldn't want to curb that. To be fair, I said to him at half-time on Tuesday night: 'You have had a yellow, no red'. He said: 'No problem'.
'He was fine. It was just with the way the game was going. I thought we'd take him off.
'I don't have a problem with Arnold. I'd be concerned about taking away that edge. That's what attracted us to him in the first place."