Ian Henderson's hopeful effort, which hauled the U's level at London Road, was their first goal on the road in 566 minutes of football.
Henderson struck after 17 minutes during an all-action opening quarter, looping a shot into the far corner with the outside of his boot after collecting a long throw from Nathan Clarke.
Peterborough went ahead after just six minutes. Keeper Ben Williams had already pulled off a double save to deny Craig Mackail-Smith and George Boyd by the time the latter drilled in a shot from the edge of the box.
Chances continued to come thick and fast at both ends with Colchester striker Kayode Odejayi steering a header wide and Lee Tomlin curling an effort against a post. And it was a similar story in the second half as only last-ditch Ryan Bennett defending denied David Mooney as he went through on goal before keeper Joe Lewis' fingertips kept out a late Henderson blast.
There was still time for late drama at the other end as Williams palmed away a Mackail-Smith rocket before also stopping a Charlie Lee header.