The Moroccan, who signed on a season-long loan from Tottenham this week, came on as a second-half substitute and set up Wayne Routledge with a neat through ball.
Magilton told the club's official website: "There's no doubt the lad can play. He's an exceptional talent and he just needs to learn when he can play with it and when he needs to give it."
Gavin Mahon was also on the scoresheet for the R's in what Magilton felt was a "good test" for his players.
"I was pleased with how we played in the first half. I thought our passing and movement were excellent at times," he added.
"That's what we've been working on in training and it was nice to see it come into our play. But at times we lacked concentration and obviously fitness plays a part in that."