QPR boss Magilton welcomes Wigan's Watson
The 24-year-old was signed for £2million from Crystal Palace in January by former Latics manager Steve Bruce, but has found himself out in the cold this season under Roberto Martinez.
"Ben will prove to be a fantastic addition to the squad," said Rangers boss Jim Magilton.
"He's got a proven track record in this division, as well as the Premier League, and I'm just delighted we've been able to bring him to the Club.
"He's a box-to-box midfielder, who scores goals and puts his boot in - he's got all the attributes that you need to play in that central-midfield role."