QPR went behind in the 38th minute to own goal from Ryan Manning before Luongo stroked home a lovely low finish to even up the match only a minute after going behind.
Luongo lasted the full 90 minutes as the home side continued their momentum in the second half - scoring three times without reply.
The Socceroo midfielder's goal means he has scored in four of QPR's last seven Championship matches.
Tim Cahill was an unused substitute while James Meredith played 90 minutes in Millwall's 2-2 draw with Ipswich Town, who handed a debut to 18-year-old Sydney-born striker Ben Folami.
Striker Tomi Juric scored from the spot as FC Luzern defeated FC St Gallen in the Swiss Super League.