West Brom turned on the style to overpower Bristol City and go back to the top of the Championship table.
The Baggies peppered the visitors' goal without reward during the first period.
But Roman Bednar broke the deadlock from close range following Carl Hoefkens' cross and Robert Koren's superb 20-yard drive made it 2-0.
Kevin Phillips rolled in a third after a defensive mix-up and he added a second from 18 yards before Darren Byfield's close-range shot made it 4-1.
West Brom manager Tony Mowbray on two-goal hero Kevin Phillips:
"Kevin has got straight back in the saddle.
"He was scoring goals every game before he was injured. He has come back and is scoring goals again. That is quality.
"He possesses class and he knows the areas to get into. He is clinical in his finishing and he was a threat all game."
Bristol City boss Gary Johnson:
"We do know that if you let teams like West Brom at you and lose your concentration and give the ball away then they will show their quality.
"They are a Premier League club in waiting. But we did not want to see that.
"Unfortunately we did see it because we had a 25-minute spell where we were poor and they were very, very good. That is what happens at this level against teams like West Brom."
West Brom: Kiely, Hoefkens, Cesar, Pele, Robinson, Gera, Koren, Greening, Morrison (Beattie 80), Phillips (Albrechtsen 86), Bednar (Miller 70).
Subs Not Used: Steele, Barnett.
Goals: Bednar 48, Koren 67, Phillips 72, 75.
Bristol City: Basso, Orr, McCombe, Fontaine, McAllister, Sproule (Skuse 79), Elliott, Johnson, McIndoe (Noble 79), Trundle, Showunmi (Byfield 52).
Subs Not Used: Weale, Vasko.
Booked: McIndoe, Fontaine.
Goals: Byfield 87.
Att: 27,314.
Ref: Martin Atkinson (W Yorkshire).
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