Shane Long marked his return from injury with the winner to lift West Brom into the top 10 and pile the problems on for Bolton.
The Baggies had gone into an early lead when Jerome Thomas beat the offside trap and rounded Jussi Jaaskelainen.
Ivan Klasnic levelled from the spot after Fabrice Muamba was fouled.
But Long headed his fourth goal of the season in the 56th minute, just four weeks after sustaining a serious-looking knee injury.
With both sides desperate for points to pull clear of the relegation zone, it was a lively start.
Chris Eagles saw his dipping volley fly narrowly over the bar and Gary Cahill had a header cleared off the line by Youssouf Mulumbu, while, at the other end Jonas Olsson and Long both went close.
Thomas was proving to be a real menace down the flanks, and it was no surprise when he put the Baggies into the lead.
Zoltan Gera's pass beat Bolton's offside trap and Thomas was on hand to fire past Jaaskelainen.
The former Arsenal winger was soon back in the thick of the action - but at the other end of the pitch.
His clumsy foul on Muamba was punished with a penalty and Klasnic calmly converted for his third goal in two games.
Both sides had chances to go into the half-time break in front, but Mark Davies failed to add a finishing touch to his mazy run and Gera could only head straight at Jaaskelainen.
The home side started to apply more pressure in the second half and it came as no surprise when they went back into the lead.
Thomas fed Nicky Shorey, who sent in a fantastic cross for Long to cap his amazing return from injury - just four weeks after chipping a bone in his knee following a controversial challenge from Aston Villa's Alan Hutton.
Bolton brought on Martin Petrov and David Ngog in an attempt to wrestle back the initiative but they too struggled to make any impact on a solid home defence.
Roy Hodgson's men were in complete control, with Thomas, Long and Gera linking up to great effect throughout the second half.
And they might have made the victory more convincing in stoppage time, but Mark Davies was spared embarrassment when he deflected a shot narrowly wide of the post.
Hodgson, speaking before the match, suggested this fixture would go a long way to deciding whether his side would challenge in the top half or be battling relegation.
On the evidence of this performance, it will be the former with Owen Coyle's men seemingly destined for a long season.
West Brom manager Roy Hodgson
"Shane Long and Zoltan Gera were excellent for us. It was a one-sided game and I think we were more than good value for the three points.
"We produced a performance we knew we were capable of.
"We were very solid defensively and we piled up chances at the other end."
Bolton manager Owen Coyle
"The game looked evenly poised at half-time but we were not at the same level in the second half.
"The game was there to win, and we had a platform to at least get a draw, but we left with nothing and that is disappointing.
"At 2-1 we were chasing the game and, as much as we pushed on, we didn't create the type of chances we did in the first half."