The R's have beaten off interest from a number of clubs to secure the former Cardiff City ace on a two-year deal.
"I'm looking forward to the challenge, there wasn't much doubt in my mind once QPR came in," said Ainsworth.
"The ambition here is above most first division clubs and I'm looking forward to giving it a hell of a go this season."
"I'm an old fashioned winger, I like to get to the line and whip it across.
"Seeing someone head in one of my crosses is just as good as scoring myself."
