Clive Platt's strike earned Colchester their eighth away win of the season at the expense of Oldham.
Play-off hopefuls suffer home defeat
Clive Platt's solitary strike earned Colchester their eighth away win of the League One season at the expense of play-off hopefuls Oldham.
A bad defensive mistake gifted the ball to Platt after just two minutes as he seized on Reuben Hazell's wayward header and fired in from 10 yards.
Colchester had a string of first-half chances with Hazell clearing off the line from Simon Hackney before David Perkins also went close.
Steven Gillespie hit the outside of the post while high-flying Oldham did not register a single shot before the break.
The nearest Oldham came to equalising was through Deane Smalley but his low shot came back off the post after 52 minutes.