One win from their previous five games had stalled the Lions' promotion push, but early goals from Derek Mazou-Sacko and Camiel Neghli meant they controlled this London derby almost from the first whistle.
Alex Neil's side moved one point above Ipswich - who host fellow promotion-hopefuls Middlesbrough on Sunday - as the race to join Coventry in the Premier League next season nears its climax.
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Millwall were ahead after just three minutes when Femi Azeez's low cross was cleared as far as Mazou-Sacko, who ran onto the loose ball to power a fine finish past QPR goalkeeper Joe Walsh from just outside the area.
It was the French midfielder's first goal for the club and it settled nerves of Lions supporters that had seen their side lose their last two home games.
The hosts were well on top and had an opportunity to double their lead by the time seven minutes had been played when Tristan Crama headed Casper De Norre's cross over.
It was a relentless opening quarter from Millwall and they celebrated their second goal in the 17th minute when Mazou-Sacko won the ball and quickly gave it to Neghli, who chopped inside before bending a lovely shot into the far corner.
Neghli then almost claimed his second after 24 minutes when he nipped in ahead of Jake Clarke-Salter to go through on goal and although he dinked his shot over Walsh, it cleared the crossbar as well.
The chances continued to come thick and fast for the Lions as Josh Coburn's header from Azeez's cross was tipped over by Walsh before Zak Sturge shot into the side netting.
QPR boss Julien Stephan made four half-time substitutions and saw his side create the first chance of the second half when one of those replacements, Rumarn Burrell, headed wide from Clarke-Salter's cross.
Morocco international Ilias Chair came on for his first bit of action since November - following injury - for the Hoops and nearly pulled one back, with a low shot from outside the area that went wide of the near post.
Millwall did not pose the same attacking threat as the first half, but they came very close to a third goal after 76 minutes when Coburn met Azeez's ball into the box before Walsh was somehow able to save with his legs.
It took QPR until the 89th minute to register a shot on target as Nikolas Madsen's effort from 25 yards was kept out by Millwall goalkeeper Anthony Patterson, who had a quiet afternoon on what was a successful one for his side.
The managers
Millwall's Alex Neil:
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QPR's Julien Stephan:
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