A last-minute Charlie Austin penalty helped Albion return to the top of the Sky Bet Championship with a fifth-successive victory.
Despite a dominant performance Slaven Bilić’s side found themselves heading into the final minute level at 0-0, but when Kyle Edwards rushed through on goal he was tripped by Declan Rudd, and Oliver Langford pointed to the spot.
Charlie Austin scored from the spot, sending Rudd the wrong way before side-footing his penalty into the bottom-right corner - creating scenes of jubilation in the away end.
Bilić named an unchanged line-up after a 4-1 victory against Bristol City last Wednesday.
The early stages saw Albion dominate possession, but it took until close to the half-hour mark to create the first shooting opportunity of the evening to excite their vocal away following.
Nathan Ferguson picked the ball up in his own half and beat his man. The young full-back powered forward and Preston’s backline parted, allowing him to rifle a shot at goal, which Rudd tipped over the bar.
The hosts went close next. Sean Maguire found himself unmarked in the Albion box following a throw-in and hit a shot which Sam Johnstone had to beat away at his near post.
Bilić’s side bounced straight back, though. Matt Phillips found a yard on the edge of the Preston box and hit a curling left-footed effort just wide before whipping in a superb free-kick to the back post which Kyle Bartley couldn’t quite turn in.
Phillips continued to be at the centre of the Baggies’ attacking intent, hitting a shot onto the turn straight at Rudd.
Albion continued to control the ball as they searched for a way past the hosts’ resolute defence, and once again Phillips found space on the edge of the box and hit a low effort, which Rudd tipped wide.
After the break, the hosts nearly provided the Baggies with the opener. Joe Rafferty tried to hook a long Kieran Gibbs clearance to safety, but nearly scored a comical own goal, only for the ball to trickle just wide of the post.
Johnstone made a save to keep the scores level, getting his fingertips to a curling effort from Preston’s Daniel Johnson and turning it round the post.
The hosts had a few more chances; Alan Browne charged on to a loose ball in the Albion box but Ferguson threw his body in front of his side-footed shot. Then from the resulting corner Jayden Shockley headed over from close range.
Bilić brought on Kyle Edwards just after the hour mark, and Charlie Austin with quarter of an hour to play as the Throstles’ search for a way through the Preston backline continued.
Plenty of possession eventually paid dividends; Kyle Edwards burst through on goal and went round Rudd, who tripped the Albion winger, with referee Langford pointing straight to the spot.
Austin stepped up to tuck the penalty into the corner, adding the perfect ending to a convincing away performance from the Baggies.
Albion: Johnstone; Ferguson, Bartley, Ajayi, Gibbs; Livermore, Sawyers; Phillips (Edwards 61), Pereira, Diangana (Austin 75); Robson-Kanu (Krovinović 84).
Subs: Bond, Furlong, Hegazi, Barry.