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 (4,5,6；42,43,44) of which a lower and upper support (4,5；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.
