Goals from the trio secured a win for the Black Cats, moving them out of the relegation zone as the Royals remain deeply rooted in it following yet another flat performance
The hosts were in control right from the outset as James McClean put them one ahead with an impressive strike after just two minutes, before Steven Fletcher eventually extended the deficit with an immaculate backheel and Stephane Sessegnon capped off the rout with a goal in the dying moments.
Sunderland made two changes from the team that suffered a 3-1 loss to Chelsea, with Fletcher returning from an ankle injury to replace Connor Wickham up front, while Jack Colback came in for Phil Bardsley, leaving Craig Gardner to deputise in an unfamiliar role at right-back.
The away side, meanwhile, made three changes from the side that endured a disappointing 1-0 defeat against Southampton, as Alex Pearce, Garath McCleary and Noel Hunt all stepped in to the side in place of Sean Morrison, Hal Robson-Kanu and Jason Roberts.
Sunderland got off to a fantastic start and had the lead in the 2nd minute, when a fairly innocuous-looking corner was flapped at by goalkeeper Federici, before falling to McClean on the edge of the box, and the winger duly slammed his effort past the melee of bodies to hand his side the lead.
This pressure finally paid off as they extended their lead in the 28th minute, after Danny Rose drove to the byline and fired the ball across the area for Fletcher to beautifully back-heel the ball goalwards.
The Royals improvemed in the second half as Mignolet was tested for the first time after an excellent Nicky Shorey free kick forced him into an equally excellent save.
The away side failed to capitalise on their pressure, though, and, with twenty minutes remaining, Sunderland looked as if they had a handle on the game, as an excellent Sessegnon snapshot produced an impressive stop from Federici.
With a few minutes left, the Belgian shot-stopper was once again called into action as a Hunt header forced another superb save out of Mignolet, with a clean sheet still in sight.
With the clock ticking down, Sessegnon duly capped proceedings off in the 90th minute after receiving a long ball, he rounded Federici to make it 3-0, compounding Reading`s misery and securing a vital win for O`Neill`s side.