It was Reading's second successive heavy defeat without scoring themselves and worryingly their only scorers this season have been defender Andre Bikey and midfielder Stephen Hunt.
They even failed to score with a penalty 15 minutes from time with Robert Green saving Kevin Doyle's kick after the keeper had tripped substitute Dave Kitson.
West Ham's win was ample revenge for their 6-0 thrashing at Reading last season - the biggest winning margin in the Premier League during the campaign.
They could have won by more with Lee Bowyer and Matthew Etherington both failing to take great chances when the Hammers were already two ahead.
The Hammers started in determined fashion and took the lead after only seven minutes.
Bowyer robbed James Harper in midfield and his instant pass sent Craig Bellamy clear.
The Welshman used his pace to stay in front in a chase with Ivar Ingimarsson and fired a shot low into the far corner of the net.
West Ham were testing referee Howard Webb to the limit with some bustling tactics early on, but despite awarding a string of free-kicks against them, he kept his cards in his pocket at that stage.
Alan Curbishley's men were relying on a swift counter attacking game and it came close to paying off again with Mark Noble having a great chance to put them further ahead only to blaze wide.
Reading keeper Marcus Hahnemann had an anxious moment when he spilled George McCartney's cross, but Etherington prodded the loose ball just wide.
Reading's brightest spell was towards the end of the first half when they threatened to get back into the game and had chances to do so.
Three minutes before the interval they almost got the equaliser. Skipper Graeme Murty chipped the ball into the goalmouth, Brynjar Gunnarsson laid the ball back into the path of Hunt and his careful shot struck the crossbar.
Early in the second half it was all over. Bellamy and Etherington exchanged a smart one-two inside the Reading penalty area and the winger beat Hahnemann with a clinical finish.
To make things worse, the closing stages saw Doyle's penalty saved by Green and in injury time Etherington completed West Ham's day with the third and final goal.