Quartararo – who rejoiced by copying Cristiano Ronaldo’s goal celebration – was aided by Alex Rins crashing out when second, giving the leader breathing space at the front of the field.
"My start was good, but unfortunately others made better. I'm so happy, because honestly, I didn't expect to make that pace. The pace was so strong," Quartararo said.
"I knew we had a little bit of extra pace from Alex. He was running so fast then he made a mistake, but the pace that we set was unexpected from myself.
"But it feels great to enjoy that track a lot. It's a unique track."
The Monster Yamaha rider now leads the way in the standings, having approached the campaign with a more positive attitude. Francesco Bagnaia ended up taking second place in Portugal with reigning MotoGP™ champion Joan Mir completing the podium.
"Yamaha made a big step compared to last year, but for more mentally I feel stronger," Quartararo explained to the media.
"I've learned a lot – last year, when the bike was not going so great, I was always thinking negatively. I've totally changed – feeling positive always.
"I arrived here and knew that the bike was working, and even those things that weren't working so well, I wasn't thinking about them. To set the pace we did was not easy, but I was focused."
Suzuki Ecstar's Mir recorded his first top-three finish in the embryonic stages of the season, a result he was happy with considering Yamaha have dominated so far with three straight victories.
"I knew that if I was unable to overtake in the last laps, it would be impossible to overtake in the straight," said Mir. "But it was a positive weekend overall.
"This is probably not the best track for me and I was able to finish on the podium, so I'm happy.
"In warm-up I felt really strong, but in the middle of the race I felt some trouble with some parts of the bike. In the last laps I managed to survive and was able to maintain a positive pace.
"This is not the best start to the championship for us, for me. But at both Qatar and here we were fighting for the podium.
"It is our goal to be fighting in Jerez and Le Mans too, then I expect to be stronger, but now I have to survive and score as many points as possible."