The 24-year-old former bricklayer almost joined Premier League new boys Hull last month but, despite failing a medical there, arrives at Loftus Road for an undisclosed fee.
Having signed for the Clarets from Swindon in 2011, Austin went on to score 45 goals in 75 starts and new manager Harry Redknapp hopes he can replicate that form for the Hoops.
"Charlie's an out-and-out goalscorer and we're delighted to have him here," the 66-year-old told the club's official website
"He's scored goals wherever he's played throughout his career and I'm very confident he'll take his game to the next level with us.
"I've got no doubt that if we give him the right service he will score a lot of goals for us.
"He's young, he's hungry and he's up for the challenge of helping us get out of this division."
Austin, who could make his debut in the season opener against Sheffield Wednesday, was equally optimistic about his future in London.
"I'm really pleased to be here," he said.
"Harry spoke to me at length about the ambition of the club and the desire to return to the Premier League and that's where I want to be as well with QPR.
"This is a really exciting time for me and I can't wait to pull on the QPR shirt for the first time.
"I'll come in, give my all and hopefully score the goals that ensure we have a memorable season."