The hosts fell behind just before 20 minutes had elapsed, Romelu Lukaku finishing off a decent move for the Baggies, with little action before halftime thereafter. The second period saw the Belgian hit the woodwork twice before eventually netting the second and seemingly securing the victory.
However, the game took an extraordinary turn when three goals in under 10 minutes, the final two coming in the closing stages, gave the hosts a massive three points and victory to remember.
The result, after QPR's draw with Tottenham earlier in the day, sees the Royals put some breathing space between themselves and the league's bottom-boys.
It took just over 15 minutes for the visitors to carve out the first chance when James Morrison forced Adam Federici into a fine save after George Thorne's cross from the right.
However the Royals keeper was helpless to deny Lukaku opening the scoring minutes later. The Belgian, on loan from Chelsea, started the move by bringing down a long ball in the middle of the field, he then shifted it on to Morrison, and continued his run into the box, before his teammate provided a simple cross that left the forward with an even simpler finish.
The remainder of the half saw very little action, however if Jimmy Kebe's touch after Danny Guthrie's searching through ball had been better, the attacker would have been left with a brilliant chance to equalize.
It wasn't though, and as it turned out Lukaku may well have doubled the Baggies' lead just a second after the second half began, however his strike was blocked by a fantastic sliding challenge by Adrian Mariappa. The Belgian did then put the ball in the back of the net, only for it to be correctly ruled out for offside.
Reading should have been level soon after, though, when halftime substitute Garath McClearly was presented with a clear chance and a virtually open goal - after Ben Foster completely missed Kebe's cross - however the midfielder's effort was vitally blocked by Billy Jones on the Baggies goal line.
The visitors responded well when Chris Brunt crossed for Lukaku, however the response wasn't quite good enough as the forward saw his effort come back off the frame of the goal.
Lukaku did, however, finally get his, and West Brom's, second goal of the game with just over 20 minute remaining. The forward received the ball from James Morrison before running at the Royals defense, which then backed off in regret as he duly slotted the ball past Federici at the keeper's near post.
The Royals launched a late surge when Kebe popped up at the back post to head McCleary's cross into the back of the net with 10 minutes to play, the delivery evading everyone else.
And the unlikely comeback was on when Adam Le Fondre slotted home a late, late penalty with just three minutes left. Olsson brought down Kebe inside the box, the forward sending Foster the wrong way.
The Madejski then erupted when, miraculously, Pogrebnyak beat two West Brom defenders to a goal-mouth scramble to put the hosts 3-2 up and secure all three points in extraordinary fashion.
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