Visiting Oldham had won three of their first four league matches of the season but they were left hanging on for a point at the death.
Ronnie Moore's men rarely threatened to score themselves with home keeper Dean Gerken forced into just one serious save all afternoon when catching a shot from Paul Warne midway through the second half.
Otherwise, it was Colchester in the box seat and they should really have secured all three points on the chances they created after the break.
Latics keeper Chris Day was the saviour for the visitors. He jumped high to claw away a goalbound header from Chris Iwelumo in the 51st minute following a fine cross from Sam Stockley.
Stockley and Greg Halford combined well down the right flank all afternoon and it was Halford who almost broke the deadlock on 70 minutes with a low drive from 20 yards that Day was at full stretch to push around his far post.
Colchester were encamped in Oldham's half during the closing minutes and big man Iwelumo should really have stole them the winner in the last minute of normal time.
Former Stoke and Brighton striker Iwelumo latched on to a flick by Halford, but he poked his shot straight at Day from point-blank range. Iwelumo was slightly over stretching but it was a chance he should have buried.
At least the point extended Colchester's unbeaten run in the league to three matches following their back-to-back defeats in their first two fixtures.
Oldham were just happy to escape from Essex with a point to continue what has been an excellent start to the season.