Defoe put Tottenham ahead in the first half before two goals in three second-half minutes secured a first win under new manager Andre Villas-Boas.
First Gareth Bale's fortuitous shot looped over Alex McCarthy to put Tottenham 2-0 up and Defoe secured victory for the Londoners after a mazy dribble.
Hal Robson-Kanu scored a late consolation for the hosts, but the Royals were second best to Spurs throughout.
Disappointing results against West Brom and Norwich had seen the pressure mount on Villas-Boas just weeks into his tenure, but Defoe believes the club are finally showing their true colours.
"New managers come into football clubs and sometimes it takes time," Defoe told Sky Sports 1.
"People just think instantly they're going to be unbelievable, but sometimes it takes time.
"I'm sure today [Sunday] the fans are happy and everyone that's been doubting us they can hopefully look at us and see that we can do well this season.
"Our season will start now."
Watch: Defoe double powers Tottenham... More Videos
Defoe could have added a third to complete his hat-trick but he was content with the three points nevertheless.
"It would have been nice to have got the match ball, but to score two and help my team win is fantastic," he added.
Former Chelsea boss Villas-Boas welcomed the three points, which came after his side spurned one-goal leads to draw their last two league outings.
"We've been chasing this win for quite some time and it's important for everybody," the Portuguese told Sky Sports 1.
"Hopefully we can shoot on from now on.
"We could have gone 2-0 up a little bit earlier as we looked bright and confident and played very, very good football."
Villas-Boas deployed Defoe in a lone role up front and was delighted with the performance of the striker, who also netted for England during the international break.
"I'm happy for Defoe to find the back of the net again. Three goals in the Premier League shows the goalscorer that he is," he said.
"And I'm happy for the team in general. They were very committed to getting our first win. It's always difficult against promoted teams.
"Hopefully this can give us a build up for the future."
Reading manager Brian McDermott conceded his side had been second-best throughout.
"The second goal killed us really. We came up against a top-class side today and they played well. They deserved to win," he said.
"We have to move on very, very quickly - you have to do that in this league.
"It's a learning curve for all of us. We know we're playing against a team of world-class individuals, and today they have played well and we didn't cause them enough problems."