(a) preselecting roof and hearth temperatures in each zone;
(b) measuring the roof and hearth temperatures in each zone;
(c) controlling the infrared heating means to maintain substantially the preselected hearth and roof temperatures in each zone;
(d) preselecting a cooking time for food products to be conveyed successively through the zone along the length of the chamber; and
(e) controlling the speed of the conveyor means to cause the food products to be conveyed through the length of the tunnel within said preselected cooking time;
whereby the food products may be rapidly, accurately and uniformally cooked according to a desired cooking profile by being differentially heated in the different zones while being conveyed through the zones in a precisely time-controlled manner.