Two Craig Dawson headers either side of Hal Robson-Kanu pouncing on David Ospina spilling a cross were too much for the visitors, whose goal came from Alexis Sanchez.
As Arsenal fans battled out over Arsene Wenger’s future with aerial protests, the Gunners found themselves utterly outclassed by a powerful, organised Albion side.
Further up the table, Chelsea travel to Stoke City for a Saturday 3pm kick-off knowing another three points would secure a minimum 10-point lead at the top heading into the final 10 games of the season.
The Blues also lost the reverse fixture last season, thanks to a solitary Marko Arnautovic goal, and are without the injured Eden Hazard.
EPL | The Premier League table after 29 matches
Chelsea's main rivals for the title, Tottenham and Manchester City, are in action on Sunday. Spurs begin life, again, without the injured Harry Kane when they welcome Southampton to White Hart Lane.
City host Liverpool in the game of the weekend, knowing anything other than a win would see them leapfrogged.
In the battle against relegation, Crystal Palace are seeking a third straight win as they welcome Watford to Selhurt Park on Saturday.
Sam Allardyce has finally got Palace settled into a rhythm, with victories against Middlesbrough and West Brom lifting the Eagles out of the relegation zone.
Hull, in 18th, are just a point off safety but travel to Goodison Park to face an Everton side looking for their sixth home win on the bounce.
Finally, West Ham welcome Champions League quarter-finalists Leicester City to the London Stadium in a busy Saturday schedule.
The Hammers board have called on Bilic and his players to improve results in a bid for a top-half finish after Joshua King's hat-trick secured a last-gasp 3-2 win for Bournemouth last time out.
Here are the Premier League matches live on Standard Sport and on TV for Gameweek 29…
|Saturday, March 18||Kickoff||Standard||TV|
|West Brom 3 Arsenal 1||12.30pm||LIVE||Sky Sports|
|Crystal Palace vs Watford||3pm||LIVE|
|Everton vs Hull City||3pm|
|Stoke City vs Chelsea||3pm||LIVE|
|Sunderland vs Burnley||3pm|
|West Ham vs Leicester City||3pm||LIVE|
|Bournemouth vs Swansea City||5.30pm||BT Sport|
|Sunday, March 19|
|Middlesbrough vs Man Utd||12pm||BT Sport|
|Tottenham vs Southampton||2.15pm||LIVE||Sky Sports|
|Man City vs Liverpool||4.30pm||Sky Sports|