The in-form striker grabbed his first after 20 minutes to put the home side in front and he doubled the lead just two minutes later.
Forster completed his hat-trick, and wrapped up the victory, with the third goal six minutes into the second half to cap a good day for Alan Pardew's troops.
Bristol City missed the chance to keep in touch with Reading after falling to a shock 3-1 defeat to struggling Northampton at Ashton Gate.
Jamie Forrester grabbed two goals in a minute (36,37), one from the penalty spot, to put the visitors in control.
Tony Thorpe pulled one back for the home side after 62 minutes, but James Hunt made sure of the win for Northampton with the third goal in the 69th minute, and lift them off the foot of the table.
Stoke also missed the opportunity to close the gap on the leaders as they lost 1-0 to Queens Park Rangers at The Britannia Stadium.
Gavin Peacock fired the winner for Rangers nine minutes from time
A hat-trick from Bobby Zamora gave Brighton a thrilling 4-3 victoy over struggling Cambridge at The Withdean Stadium.
Gary Hart fired the home side in front after 25 minutes, but Cambridge drew level just two minutes later through Shane Tudor.
Zamora grabbed his first from the penalty spot after 50 minutes for his 50th goal for Brighton, but Luke Guttridge again equalised for the visitors four minuts later.
Brighton regained the lead through Zamora in the 75th minute, but Cambridge again came back to equalise in the 81st minute with a penalty from Paul Wanless.
It looked like that might be enough to give the visitors a point, but Zamora popped up to steal the win with his third goal two minutes from time and send Cambridge to the bottom of the table.
Wigan ended Brentford's unbeaten home record with a hard-fought 1-0 win at Griffin Park.
Andy Liddell netted the only goal of the game after 79 minutes.
Oldham maintained their pursuit of the leading pack with a 3-1 win over Wrexham at Boundary Park.
Andy Morrell fired the visitors in front after just 11 minutes, but Paul Murray drew the sides level in the 34th minute.
Veteran midfielder John Sheridan grabbed the second from the penalty spot after 56 minutes and Wrexham's woes were compounded with Brian Carey being sent-off soon after.
Canadian striker Carlo Corrazzin wrapped up the win with the third goal in the final minute
Cardiff got back to winning ways with a superb 1-0 win over Wycombe at Adams Park.
Irish midfielder Graham Kavanagh hit the only goal of the game to give The Bluebirds all three points and end Wycombe's unbeaten home record.
Port Vale ensured it was a not a happy home debut for new Notts County boss Billy Dearden with a convincing 3-1 win at Meadow Lane.
Stephen Brooker hit two goals for the visitors (16 and 76) and Stephen McPhee hit the other for Vale from the penalty spot after 38 minutes.
Nick Fenton pulled one back for the home side four minutes from time, but it proved to be nothing more than a consolation.
Tranmere kept in touch with the leaders with a hard-fought 1-0 win at Bury.
Jason Koumas hit the only goal of the game after 28 minutes to give the visitors all three points.
Chesterfield continued their climb up the table with a superb 2-1 win at Colchester.
Jamie Burt fired the visitors in front after 17 minutes, but on-loan signing Graham Barrett hit back for the home side four minutes into the second half.
Glynn Hurst netted the winner for Chesterfield after 75 minutes.
Bournemouth remain in trouble after going down to a 3-2 defeat to Huddersfield Town at Dean Court.
Andy Booth put the visitors in front after just 3 minutes and Chris Hay doubled the lead after 24 minutes.
Leon Knight hit the third in the 37th minute to put Huddersfield in firm control.
Derek Harris pulled one back for the home side after 58 minutes and Warren Feeney made the visitors sweat with the second two minutes from time, but Huddersfield held on for the win.
Swindon grabbed a valuable point with a 1-1 draw at Peterborough.
Eric Sabin gave the visitors the lead after 20 minutes, but Jimmy Bullard earned the home side a point with the equaliser in the 59th minute.
Click on a fixture for the full match summary:
Bournemouth v Huddersfield
Brentford v Wigan
Brighton v Cambridge
Bristol City v Northampton
Bury v Tranmere
Colchester v Chesterfield
Notts County v Port Vale
Oldham v Wrexham
Peterborough v Swindon
Reading v Blackpool
Stoke v QPR
Wycombe v Cardiff
Click here for updated league table
