The home side began brightly, with Bryan Ruiz testing Jussi Jaaskelainen early on.
The Finn was equal to it, but he could do nothing to stop Dimitar Berbatov from grabbing the opener in the 9th minute.
Poor marking allowed the Bulgarian an unchallenged header at the back post, and he duly nodded home.
The Cottagers kept going forward and nearly got a second through Damien Duff, but his shot went just wide of the post.
Berbatov then clipped the outside of the post from 25 yards out just before the break.