The Baggies' goal difference meant they had effectively sealed promotion prior to their final-day visit to west London.
But goals from Kim Do-heon and Chris Brunt rubber-stamped their return to the Premier League and ensured they ended the season as champions.
Mowbray said: "This is a proud moment. When you think back to when we lost to Burnley on the opening day, we've come a long way and made a lot of progress.
"Credit to the players who have won more games and scored more goals than anyone else and rightly ended up as champions.
"There's a great debate in football about whether it's all about winning or all about entertaining. There's got to be a balance and we've got that balance right."
Mowbray, who plans to open talks with out-of-contract duo Zoltan Gera and Kevin Phillips, pledged to continue his attacking approach next season.
"Hopefully we'll have a good shot at it at the next level," he said.
"You do need to adjust in the Premier League. There are better players there and you need to have a gameplan, but we'll still go out to try to win matches.
"There will be times when we play against better teams, but there are also times when we can surprise teams and put them onto the back foot."
The game at Loftus Road swung in Albion's favour after the 38th-minute sending off of QPR's Martin Rowlands, who was controversially shown the red card following a crunching challenge on Jonathan Greening.
The dismissal hit Rangers hard and it came as no surprise when the Baggies went ahead seven minutes after half-time.
Gera went past Damien Delaney and cut the ball back from the right, giving Korean midfielder Kim - on as a substitute - the easy task of heading home.
Brunt hit the bar with a curling 25-yard effort before finding the net with a fabulous free-kick that crushed any prospect of a Rangers fightback.
QPR coach Luigi De Canio was furious about the dismissal of Rowlands and launched a scathing attack on referee Paul Taylor.
De Canio said: "We prepared ourselves for a great game so that we could celebrate the end of our season, but I sincerely believe the referee ruined the whole game.
"He demonstrated that he was in no way up to the situation and I'm not only talking about the red card but the whole game. He offended me, he offended the fans and he offended my players.
"I didn't think it was a red card but I'd like to say well done to West Brom. They showed today and throughout the season that they were the best team in the Championship and are worthy winners.
"It would be fantastic to be where West Brom are this time next season. At the moment it is difficult to evaluate how close we are to that, but I consider this season to be extremely positive."