Rangers were in front inside two minutes through Gareth Ainsworth's drive but David Healy chipped in to level seven minutes later.
Deane put Leeds ahead on 13 minutes, and Jermaine Wright swept home to make it 3-1 just 10 minutes later.
Deane then scored two in two minutes before the break to complete a hat-trick and hit his fourth on 72 minutes.
QPR boss Ian Holloway
"The doorman asked me if I had a pass - we didn't have a pass all day!
"I should have stayed at home. It may be a virus or food poisoning. I thought things couldn't get any worse, then we let in six goals after being one up.
"It looks like we got Leeds really annoyed. They played superbly and we were a shadow of what we can be."
Leeds: Sullivan, Kelly, Carlisle, Butler, Pugh,
Walton (Richardson 90), Gregan, Wright, Oster,
Deane (Lennon 86), Healy (Joachim 77).
Subs Not Used: Carson, Kilgallon.
Goals: Healy 9, Deane 13, Wright 23, Deane 42, 44, 72.
QPR: Day, Bignot, Shittu, Santos, Rose (Padula 11), Ainsworth,
Bircham, Gallen, McLeod (Cook 45), Furlong, Cureton (Bean 45).
Subs Not Used: Branco, Miller.
Goals: Ainsworth 2.
Ref: C Webster (Tyne & Wear).