Edwin van der Sar made two fantastic saves to deny Victor Moses and James McCarthy either side of Javier Hernandez's 17th-minute opener.
The Mexican profited from Wayne Rooney's excellent through-ball after half-time to double United's lead with his 13th goal of the campaign.
After that it was a cruise, with Rooney presented with a tap-in by Dimitar Berbatov's unselfishness and Fabio wrapping up a win that takes United four points clear of Arsenal at the start of a crucial week in the title race.
"It is a good result because this is a difficult place to come," said Ferguson, whose words ignore the fact United have won all 13 meetings with their north-west neighbours.
"For the first 20 minutes, Wigan were terrific. Van der Sar made three great saves and another fantastic one in the second-half."