Two second-half goals were enough to ensure safe progression for the Red Devils who will face either Middlesbrough or Chelsea in the next round of the competition.
Second-half goals by Nani and Javier "Chicharito" Hernandez were enough for the hosts to claim the win, despite a late goal from Jobi McAnuff, and the Red Devils march on to face either Chelsea or Middlesbrough.
The hosts got off to a flying start and might have opened the scoring in the opening minutes. Almost straight from the first kick Chicharito saw a low shot blocked but neither Danny Welbeck nor Antonio Valencia was able to slot the loose ball home.
Less than a minute later, Welbeck went close. Some clever work by Ashley Young saw him slip the ball through to the striker, but his low shot was saved by Adam Federici.
Reading slowly came back into the game, pressing United high up the pitch and looking a real threat at set pieces. United had the returning Nemanja Vidic to thank on 17 minutes as the center back did superbly to head Nicky Shorey’s free kick to safety with Sean Morrison poised to head home.
As the first half drew to a close United was forced into a change with Phil Jones hobbling off, after a strong challenge by McAnuff. Substitute Nani made an instant impact on the game, smashing a right-footed volley across goal and onto the post before forcing Federici into another good stop with a stinging left-footed shot as the hosts ended the half strongly.
The hosts emerged after the interval with a greater tempo but struggled to convert their greater urgency into clear-cut chances, leading to the arrival of Robin van Persie for Young just after the hour mark.
The Dutchman’s arrival helped United take almost complete control of the game, forcing Reading further and further back until finally the Royals’ resistence was broken.
With 69 minutes on the clock, Valencia carried the ball down the right, before passing to Nani in the box, where he took one touch before poking past Federici to break the deadlock.
Minutes later, the game appeared effectively over as a contest as United grabbed a second. Again the danger came down the right, this time through goalscorer Nani, who crossed for Chicharito to nod home at the near post and double United’s lead.
Wth 10 minutes to go, a lapse in concentration in the United defense set up a nervous finale after McAnuff pounced on some awful defending to drive past De Gea from close range.
Reading have made late comebacks their speciality at times this season, but on this occasion there was to be no fairytale as United held on to continue to fight on three fronts, while the visitors must concentrate on avoiding relegation from the Premier League.