Well took the lead with their first real attack on 16 minutes when a Scott McDonald cross was turned goalwards by Killie defender Frazer Wright.
Keeper Graeme Smith did well to keep this deflection out but Richie Foran reacted quickest to force the ball over the line from a yard out.
Four minutes later the home side were two up. A Jamie Paterson corner was met by Killie's David Lilley and Well's Mark Reynolds and ended up in the visitors' net with the young Well man claiming his first senior goal.
Well fans were pinching themselves on 24 minutes when they made it three, McDonald cut the ball inside to Paterson who then laid it on to Brian Kerr, who sent a first-time shot from 25 yards searing past Smith.
With eight minutes left to play McDonald finally got the Steelmen's fourth goal when he somehow found space in the box to head a Paterson corner past Smith from just six yards out.
The Aussie made it five four minutes later when he held off Wright to shoot low past a stranded and bewildered Smith.