A mullion assembly for a refrigerator cabinet has a pair of adjacent edge wall insulating gasket members extending toward the open side of the cabinet. The edge wall members each have a forward surface extending flush to the open side for supporting a portion of a door sealing gasket and a recessed channel extending rearwardly of the open side. One of the edge wall members has a locating flange member with an edge portion extending toward the other one of the edge wall members. A metallic mullion bar extends between the pair of edge wall members and has a flat wall portion against which seals another portion of the door sealing gasket carrying a magnet. The mullion bar has rearwardly extending flanges extending into and supported by a respective one of the recessed channels of the edge wall members. A block of fiberglass insulation is mounted rearwardly of the metallic mullion bar within the space between the interior cavities. The insulation member is held in engagement by and between the pair of edge wall members by the locating flange member edge portion urging the insulation member against the other edge wall member. This assembly has reduced thermal transfer from outside ambient to the interior cavity of the cabinet through the metallic mullion bar.