The 20-year-old had not worn the No10 jersey since playing for his club side Hawick before moving on to Glasgow Warriors.
But he orchestrated affairs to impressive effect as Warren Gatland's men notched up 10 tries just a week-and-a-half out from the first Test against the Qantas Wallabies.
"He's got natural talent," said Howley.
"He's a great footballer, has great feet and not a bad kicking game either. I thought he facilitated the centres and our backline particularly well.
"We wanted to play nice and flat and he played right on the cliff.
"He gave opportunities to Jamie (Roberts) and Dricko (Brian O'Driscoll) and the outside backs so I was delighted with Stuart because he can play there."
The Lions raced into a 38-0 half-time lead in Newcastle and Howley was pleased with the first 40 minutes of the victory.
He was left a little frustrated with a less assured second-half display, but he insists The Lions will learn from their latest run-out and continue to improve.
"I'm happy with the first half, but a bit frustrated with the second," said Howley.
"Obviously, it was a bit dewy, but there was probably a few too many handling errors for our liking, particularly in the opposition 22.
"It was frustrating, but I'm happy we've scored 10 tries and seen some combinations tonight and others coming off the bench.
"You lose continuity for obvious reasons, but we are generally happy.
"Our goal was to be clinical. We had to bring our own intensity to the game because, as we're all aware, the intensity of that first Test match is going to be huge.
"We had a great run-out against the Reds on Saturday, but we had to bring our own intensity to the game tonight. We've probably come up short of that. But to come away and nil them has left (defence coach) Andy Farrell pretty happy. I suppose that was key as well."