Zoltan Gera put the Baggies in front in the 32th minute after a fine pin-point cross from the rapidly improving Chris Brunt. Albion's make shift defence, which included first-team debutants, Shelton Martis, Jared Hodgkiss and goalkeeper Luke Steele, kept the Foxes at bay until a highly disputed equaliser 15 minutes from time.
However, the visitors were not to be denied as Scottish International Beattie latched on to Pele's through ball and curled an unstoppable shot in to the top left hand corner of City 'keeper, Fulop's goal to send the away fans and bench into celebration.
"I think we richly deserved the three points," Mowbray said after the victory.
"The best team won.
"In my eyes, it would have been an injustice had they got a point from a goal like that.
"I need to see it again but it was a very obvious foul to me when you look at it in the context of others that are given.
"When the referee gives a massive decision like that, it is very, very disappointing.
"Ultimately, justice was done in the context of the game."
Mowbray saved special praise for the defensive unit which was only denied a first clean-sheet in four games after what looked like a clear foul by Iain Hume on rookie 'keeper Luke Steele.
"Four out of the back five were changes," the Albion boss continued.
"We're delighted - but that's what your squad is for.
"You hope you don't have to make so many changes at once.
"You hope that one player comes in and gets looked after by the rest of the defensive unit.
"We made a lot of enforced changes today and they showed great determination to get a result.
"It was a big ask for them but the defensive unit we put together stepped up to the mark and got the job done.
"You're always hoping for a positive in adversity and for the players to step up and give you a selection headache for when everybody's fit.
"Pele's showed his quality and composure at centre-half and Jared Hodgkiss is just a good footballer - wherever I ask him to play."