The 26-year-old midfielder left Real Madrid for west London last August in a reported £9million deal but could not help Harry Redknapp's men avoid relegation from the Premier League at the end of the 2012/13 season.
"The 26-year-old midfielder has penned a season-long loan deal with the La Liga outfit.
"Granero, of course, joined QPR from Real Madrid last summer and has since made 28 appearances in all competitions for the Rs, scoring one goal.
"The deal is subject to international clearance."
For the big stories and the banter follow us on Twitter: @tribalfootball