Alvaro Morata scored his eighth Premier League objective of the season when he changed over a bounce back after Albion goalkeeper Ben Foster had parried Eden Hazard’s low shot.
Danger made it 2-0 not long after when he gathered Morata’s flick and took the ball around Foster, before Marcos Alonso volleyed in a third from Cesc Fabregas’ free-kick.
In the second half, Hazard scored his second of the diversion with a twisted complete from 18 yards out after another magnificent Fabregas pass.
The triumph was Chelsea’s fourth progressive association win, while West Brom stay without a win in all rivalries since 22 August, a keep running of 11 amusements.
Chelsea climb to second, yet they will drop down to third if Manchester United beat Newcastle in the late diversion.