A spiral oven and a method of cooking a food product in a spiral oven using a cooking medium wherein (a) the food product is conveyed within the oven cooking chamber by a spiral conveyor having a plurality of spiral flights and (b) the cooking medium is discharged either upwardly and/or downwardly within, or laterally into, one or more vertical gaps between adjacent pairs of spiral flights using one or more delivery duct structures which extend inside the interior of the cooking chamber.