A disposable food bag for use with a food tray which has a base of a predetermined length L and a width W, a wall extending upward from the base of a predetermined height H forming a container to provide a predetermined depth D and having a upper perimeter lip, wherein the bag includes a plastic substrate of length L1 which is slightly larger than length L and a width W1 which is slightly larger than width W and has an outer portion is configured to be retained by the perimeter lip, and an inner portion which when the outer portion is so retained has a depth D1 approximately the depth D and has at least one vent opening disposed within the inner portion.