Austin was on hand to convert from the spot to secure the Baggies a fifth successive victory and move them back above Leeds.
Slaven Bilic’s side looked set to rue a number of missed opportunities in the first half as they struggled to break through a resilient Preston defence.
But Austin’s spot-kick moves them two points clear of Leeds, while Preston slipped to a third successive defeat as their unbeaten home record in the Championship came to an end.
The visitors were much the better side in the first half and Bilic would have been frustrated his side failed to lead at the break.
After a sedate opening, Nathan Ferguson had the first effort on 22 minutes. The right-back’s surging run carried him from his own half to the edge of the Preston box but his fierce drive was tipped over by Declan Rudd.
That break sparked the Baggies into raising the tempo and more chances followed. Matt Phillips picked up the ball following a corner and curled a left-footed effort just wide from 22 yards.
Phillips then turned provider just after the half hour mark as his pinpoint free-kick from the right found Kyle Bartley unmarked at the far post, but the centre-back inexplicably side-footed wide with a clear sight of goal.
Scotland international Phillips’ turn and shot inside the area after 35 minutes was comfortably held by Rudd, before his powerful low drive was tipped around the post.
Preston’s only opening of a disjointed opening 45 minutes fell to Sean Maguire, who broke in behind from a throw, but the Republic of Ireland striker fired straight at Sam Johnstone from a tight angle.
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