Walcott struck after just 20 seconds at Loftus Road, with the Premier League's fastest goal of the campaign enough to lift Arsenal up to third spot.
The England international is enjoying his best season in front of goal and Wenger outlined why Walcott has improved over the past 12 months.
"His finishing is better, in his duels he is stronger and he plays with more belief," Wenger told ESPN.
"You get to a stage where you're 24, which he is now, that's when a player becomes really more mature and you've seen that with his goalscoring record."
Arsenal are now two points ahead of Chelsea and Tottenham Hotspur in the race for UEFA Champions League qualification, but have played two games more than the Blues and one more than their north London rivals.
Wenger added: "Ideally, mathematically you would like to be there without anyone catching you, but it's interesting for everyone in the Premier League.
"For a long time I said that it would be the team with the most consistency. We had a difficult away game today which we won. Now, let's win at home."
The Arsenal manager also praised the performance of Queens Park Rangers, who were playing for the first time since relegation to the Championship was confirmed last weekend.
"The three points were vital for us today and it was a very difficult game," said Wenger.
"I must say, for me, QPR is a good side. If they keep the players together they can come up straight away again."