Two goals from Theo Robinson and one from Harry Pell gave Colchester a 3-1 away win at Leyton Orient, for whom Ruel Sotiriou netted a consolation.
The victory took the U's into the play-off places on a rain-swept afternoon at Brisbane Road.
Colchester dominated for much of the game and Pell had seen a header cleared off the line in the first half before Robinson scored after fine work down the right side by Ryan Jackson in the 41st minute.
Jackson crossed into the box where the unmarked Robinson was able to stab home to give the visitors a deserved lead.
The U's continued to dominate and Kwame Poku struck a post just after the break before Luke Gambin was denied by a fine save by Sam Sargeant.
Pell doubled Colchester's advantage in the 64th minute when O's keeper Sargeant parried a cross and the midfielder netted from close range.
Orient responded with Matt Harrold and Jordan Maguire-Drew going close before substitute Sotiriou reduced the deficit in the 86th minute.
But Robinson was to have the last word and he secured the points when he curled a shot into the net in added time.