Millar doubled the lead just 60 seconds later, following up after Cooper’s initial shot had been cleared into his path to be left the simple task of finishing from six yards.
Loughgall’s best chance of the first half came on the half hour but striker Jay Boyd was unable to keep his powerful header, from a Caolan McAleer cross, under the crossbar.
They did pull a goal back, however, midway through the second half through substitute Ferris, only on the pitch a matter of minutes.
Jay Boyd was adjudged to have been bundled over in the box by referee Ben McMaster and the big striker did the rest, blasting his spot-kick past Chris Johns.
But it was another substitute – Linfield’s Allen – who made the game safe for the visitors with a brilliant individual late effort, with the midfielder cutting in off the wing to pick his spot past a helpless Gartside.
It’s now over to Ballymena United, who host Coleraine on Saturday, to see if they reclaim their place at the summit while Loughgall remain four points adrift at the bottom after an eighth straight defeat.