Sir Alex Ferguson's Reds made light work of the test by the Thames with Danny Welbeck sweeping in a left-wing cross by Nani after only five minutes.
Nani scored the second himself, with a rare header for the Portuguese winger, after Ryan Giggs whipped a dangerous ball into the Cottagers' box.
Giggs claimed the third, although his strike took a deflection off Philippe Senderos to loop over David Stockdale and into the net, as Nani racked up another assist during a one-sided first half.
With the '12 Cantonas' song being belted out down by the Thames, Wayne Rooney took aim and unleashed a thunderbolt to make it 4-0.