The 22-year-old Canadian free agent, whose deal at Blackburn had expired, is the seventh new arrival as Rangers continue rebuilding.
Rob Green, Ryan Nelsen, Fabio Da Silva, Ji-Sung Park, Samba Diakite and Andy Johnson have already signed.
Hoilett: "The manager played a big part in my decision to come here.
"He's someone I know well here having worked with him and his backroom team at Blackburn.
"I signed my first professional contract under him and I will always remember that and be grateful to him.
"Working under such a great manager will help me to develop my skills and further my career.
"QPR are a club that are certainly heading in the right direction."
Hughes: "Junior is a player I know very well. He was just a young boy trying to make his way in the game when I had him at Blackburn.
"It was difficult for him then because of work permit issues, but I had him training with the first team very early on because his talent was there for all to see.
"We knew then he was going to have a great future and he's showed that talent over the last few seasons at Ewood Park.
"He's a player that will enhance what we've got in the group and I'm delighted he's chosen to come to us."