Cottagers boss Slavisa Jokanovic made 11 changes after seeing his side win their first Premier League game of the season.
But it didn't impact the west London club too much as they cruised past the League Two club.
"We must be satisfied after winning the game," said Whites boss Slavisa Jokanovic.
"The team showed the great ambition for fighting and pushing for the victory, for another side we are in some kind of process and we can still do a better job.
"We can be in tactically better positions and not complicate so much.
"We can play faster and with less touches, it's probably we complicate and we can show more quality today than we showed in this game.
"We are in some kind of the process, the process is going in some natural way and I hope and expect we are going to play better football next round."