The goals for the home side came from Heidar Helguson, Hogan Ephraim and Jamie Mackie.
Cardiff City are level on points with the R's thanks to a 2-0 home win over Hull City, with Seyi Olofinjana and Gavin Rae the goalscorers for the Bluebirds.
Ipswich Town were held to a goalless draw at Portsmouth, while Leeds United came from behind to secure a 2-1 win at home to Swansea City - with Bradley Johnson and Lucciano Becchio on target.
Norwich City also turned things around against Barnsley at Carrow Road, with a late Chris Martin strike sealing a 2-1 success for the Canaries.
Reading eased to a 3-0 win over Crystal Palace, with Shane Long, Ian Harte and Jimmy Kebe the goalscorers at the Madejski Stadium.
A late George Friend effort rescued a point for Doncaster Rovers from a 2-2 draw at Watford, while Nottingham Forest and Millwall drew 1-1 at the City Ground.
In the early kick-offs, Coventry City and Leicester City drew 1-1 at the Ricoh Arena, and a Richard Cresswell strike earned Sheffield United a 1-0 win at Derby County.
Burnley came from 3-1 down to defeat Preston North End 4-3 at Turf Moore, with Chris Iwelumo scoring a hat-trick.