The first half was pretty even with both sides having chances to score, Sutton coming closest with a chance that came back off the post.
O’s, missing eight players through injury and suspension, took the lead midway through the second half when midfielder Jack Parker was fouled in the box. He got up and coolly finished the spot kick to give the O’s the lead.
After the goal, the visiting side threw caution to the wind and attacked regularly but the hosts held out for their first clean sheet of the season and a place in the second round draw.