Onuoha has signed a four-and-a-half-year contract with Rangers and joins the club for an undisclosed fee.
Onuoha had long been linked with a move to link up with his former City boss Mark Hughes at Rangers.
"Nedum is a player I know well," Hughes told QPR's official website ahead of a possible debut in the FA Cup against Chelsea.
"He did very well for me at Man City and played a number of games, probably more than under any other manager.
"He is very versatile. He can play centre-back or right-back, and has good pace. He is a very good addition to the squad.
"I think he is more than competent in both positions. As a centre-back, he is strong and quick, and he can attack the ball.
"In the full-back position, he can get forward and use his pace in wider areas, so he's a great player for us to have. He offers versatility, which I like."
"He is a young man who needs to get back on track and start playing games," continued Hughes.
"We will reap the benefits of that, because he is a determined individual who wants to be a fixture in the side if he can.
"Both he and Taye (Taiwo) are similar in that they have come here, because they want to play regular football. And I think that's important.
"When you bring players into the squad you want them to be hungry and ready to make an impact.
"Both these players are good guys who are desperate to do well."