An oven serves for heat-treating food pieces laid upon a grid (13) in a cabinet (1) by means of a heat source (34). The grid consists of an upper part (13) of an endless chain running around a number of chain supports ( 42, 43, 44) of which a lower and upper support (42, 43) is defining a lower and upper end of said upper chain part. Portions of food pieces can by means of the oven quickly and easily and in a simple and economical manner be heat-treated in rapid succession. The direction of rotation can be reversed for discharge of the food pieces.
