Heidar Helguson and Collins John both scored braces to inflict more misery on under-fire Baggies boss Bryan Robson, whose side slipped to 17th place.
It was a goal-feast as Fulham stepped on the gas leaving West Brom, who grabbed a consolation through Kevin Campbell five minutes from time, feeling flat.
Helguson put the Cottagers ahead in only the fourth minute, in emphatic style.
The £1.1million signing from Watford latched on to Brian McBride's knock down before firing the ball past Tomasz Kuszczak to grab his seventh goal for the club.
Four minutes later Fulham could have doubled their lead through Carlos Bocanegra. The American jumped highest in the West Brom box but his header was straight at Kuszczak.
Albion pressed for an equaliser with Junichi Inamoto bossing the midfield and trying to carve out a chance to score against his former club.
But it was former Southampton midfielder Nigel Quashie who came closest to levelling the scores with a blistering strike from the edge of the area which Antti Niemi did well to tip over.
McBride was causing all sorts of problems for the West Brom defence and he was denied a clear goal-scoring opportunity when Kuszczak made a brave save.
Quashie again tried his luck from distance and Helguson was unfortunate to see his shot saved at the other end on 35 minutes.
But he did not have to wait long for his second. Simon Elliott's free-kick was perfect for the Iceland international, who kept his cool to head past Kuszczak.
After the restart West Brom threw on Nathan Ellington in place of the ineffective Geoff Horsfield.
But any hopes of getting back into the game were killed off when Tomasz Radzinski made it 3-0 with his first goal of the season.
The Canadian beat the offside trap to latch onto Steed Malbranque's pass before lofting the ball over the Kuszczak.
Three became four when Helguson's shot was deflected into his own net by Curtis Davis.
The bemused Robson chose to replace Kuszczak with Russell Hoult in a bid to halt the onslaught.
But Hoult suffered a similar fate to Kuszczak and soon found himself picking the ball out of his net when substitute John scored a fifth. The Dutchman steered in McBride's cross for his eighth goal of the season.
Campbell grabbed a consolation goal for West Brom in the 85th minute, much to the delight of Albion's travelling support.
But their ironic cheers were soon subdued as Fulham completed the rout with a sixth. John bagged his second of the match after Radzinski supplied the cross.