Simon Church scored two and Alex Pearce one as Reading eased to victory over a West Ham side reduced to nine men.
Joey O'Brien was sent off for two yellow cards in the 65th minute and Pearce made the visitors pay a minute later by scoring from eight yards out.
Substitute Church tapped home Adam Le Fondre's chip for his first before Jack Collison was dismissed for a wild challenge on Jimmy Kebe.
Striker Church nodded home Ian Harte's set-piece to complete the scoring.
West Ham would have gone joint top with Championship leaders Southampton if they had won the match, but were on the backfoot from the start.
Noel Hunt almost gave the Royals the lead early on while Kebe and Jem Karacan also went close to scoring in the first half.
Collison blazed over the bar for the Hammers while Papa Bouba Diop thought he had had poked the ball home but Hunt cleared off the line.
The game's scrappy nature continued into the second half before the match exploded into life after O'Brien tripped the dangerous Jobi McAnuff to earn his second yellow card.
From the free-kick given for O'Brien's offence, Harte's delivery was not cleared properly, McAnuff slipped the ball into Pearce's path and the centre-back side-footed home.
Reading dominated from there onwards and went two up when Church tapped home.
West Ham lost all their shape and discipline and were reduced to nine men when Collison needlessly fouled Kebe.
From the resulting free-kick Church headed home Harte's cross to intensify the misery for the Hammers.
Reading boss Brian McDermott:
"We are a team that's trying to evolve and we have done that today to the best team in the division.
"They have a lot of Premiership players in their side and you can see why they win so many away games.
"We are all about the team at Reading and never about the individuals. I try to explain that to players who don't play."
West Ham manager Sam Allardyce:
"Unfortunately a loss of control by the players that I haven't seen before in my time here, particularly Joey O'Brien, cost us a result today.
"It's not like him and he's not that sort of character. Then we let the opposition score from the free-kick instead of organising ourselves to see it out to a 0-0 draw.
"I wouldn't really quibble about either sending-off but if Jack Collison went then I think Noel Hunt should have gone. He caught Joey and could easily have broken his foot or leg.
"We are in serious trouble now player-wise and will be struggling to get 11 out."
Reading 01 Federici 05 Pearce 17 Gorkss 23 Harte 24 Cummings 04 Karacan Booked 08 Leigertwood 11 McAnuff 14 Kebe (Robson-Kanu - 88' ) 09 Le Fondre 10 Hunt Booked (Church - 65' ) Substitutes 31 Andersen 07 Tabb 19 Robson-Kanu 28 Antonio 18 Church West Ham United 01 Green 03 McCartney Booked 05 Tomkins 15 Faye Booked 18 Faubert 20 Demel (O'Brien - 4' Dismissed after an earlier booking ) 04 Nolan 10 Collison Dismissed 16 Noble 21 Diop (Cole - 57' ) 30 Piquionne (Carew - 72' ) Substitutes 29 Stech 17 O'Brien 09 Cole 11 Carew 19 Sears