Charlie Austin's 90th-minute penalty sent West Brom back to the Championship summit with a 1-0 win at Preston.
Austin converted from the spot on Monday 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.
"I'm an experienced cool head and I know what I'm doing," Austin told Sky Sports.
"I had a look at the 'keeper and sent him the wrong way.
"We've got great youngsters, we're top of the league and it's an exciting future for us."