Abstract: A prefabricated insulated panel includes a sheet-like face member and an insulating mat extending along one surface of the face member. Complementary male and female formations extend along opposed edges of the face member and are adapted to matingly couple adjacent panels to form a contiguously extending insulated wall structure. The face member has an upstanding flange which is offset from one of the edges of the face member and which cooperates with such edge to define a recess adapted to receive the insulating mat of the next adjacent panel therein. The flange is adapted to facilitate attachment of the panel to a support and in a manner aiding in preventing heat flow through the panel. Each panel has a side edge structure which is constructed and arranged to minimize heat transmission through abutting side joints of adjacent panels while, at the same time, allowing for expansion and contraction of the panels.