Goals by Shane Long and Gareth McAuley ended Everton's 11-game unbeaten run in the Barclays Premier League as West Brom wrapped up a Merseyside double with a 2-0 win at The Hawthorns.
Albion took their points tally to seven from a possible nine at the start of the season as they followed up their opening-day win over Liverpool with another emphatic victory.
Long made it three goals in four days - after his brace at Yeovil in the Capital One Cup - as he converted a low cross from substitute Peter Odemwingie before McAuley headed home from a set-piece to condemn Everton to a first league defeat since March.
Everton controlled the early stages and McAuley blocked a shot from Steven Pienaar.
Albion came close to taking the lead after 29 minutes, Liam Ridgewell supplying a cross which was met by Long but his header thumped against the crossbar.
Everton threatened again when Marouane Fellaini peeled away from his marker at the far post only to send his header over the bar from a Tony Hibbert cross.
Albion went close a minute before half-time, James Morrison finding himself with only Tim Howard to beat after a great run but the goalkeeper stood up and beat away his fiercely struck shot.
Fellaini had Everton's best chance after 55 minutes after Phil Neville had headed a clearance from Ridgewell back into the box. The Belgian turned sharply to create the opening but dragged his shot wide of goal.
Long broke the deadlock after 65 minutes. Ridgewell found Odemwingie in space on the left flank and his low cross picked out Long who got in front of Sylvain Distin to steer the ball past Howard.
With seven minutes left McAuley sealed the win with a glancing header from a Chris Brunt corner.