The former Everton forward has been back in training for around a week since recovering from a hamstring problem, and lined up against Brentford reserves tonight.
"I was delighted to be back out there," Johnson told the club's website. "I felt good, I felt sharp and it was a good run-out for me.
"It was important for me to get some minutes under my belt. I've been back in training for over a week now and I feel fine to be honest.
"I was only out for four weeks, it was only a minor hamstring injury, but it feels good to be back playing again."
QPR's Elite Development Squad won the match 4-0.