An air impingement oven having a conveyor belt assembly for moving food through a heat treatment passage. The air impingement oven has a fan, a supply duct, a plenum and a number of jet fingers being disposed above the conveyor belt assembly. The jet fingers have a base portion having a number of orifices for directing the impingement air onto the food. The orifices have an improved configuration. The improved configuration intensifies the airflow on the food to penetrate heat into the food surface thereby improving heat transfer. The improved configuration reduces a cooking time of the food in the air impingement oven.