An oven comprising a cooking chamber configured to receive a food product and an air circulation system configured to provide heated air into the cooking chamber comprising: - a plenum disposed proximate to the cooking chamber and separated from the cooking chamber by a back wall of the cooking chamber; - an airflow generator configured to draw air from the cooking chamber through a chamber outlet port and discharge the air into the plenum; and - an air heater (322, 214) configured to heat at least some of the air in the plenum prior to a portion of the air entering the cooking chamber from the plenum via air delivery orifices; wherein the chamber outlet port comprises outlet perforations combining to form a first geometric shape centered on an axis of the airflow generator, wherein the air delivery orifices comprise a first set of inlet perforations disposed near the top of the cooking chamber and a second set of inlet perforations disposed near the bottom of the cooking chamber, which sets each form strips of perforations, the first and second sets of inlet perforations (350, 355) combining to form respective second and third geometric shapes that are disposed on opposite sides of the outlet perforations, and wherein the second and third geometric shapes are different than the first geometric shape, characterized in that the strips of perforations (350, 355) are formed from individual rows of perforations that extend linearly along a direction substantially parallel to the plane in which the top or bottom of the cooking chamber lies, that the number of rows of perforations that form the second set of inlet perforations is larger than the number of rows that form the first set of perforations, and that the center of the outlet perforations is closer to the second set of inlet perforations than the first set of inlet perforations. - a plenum disposed proximate to the cooking chamber and separated from the cooking chamber by a back wall of the cooking chamber; - an airflow generator configured to draw air from the cooking chamber through a chamber outlet port and discharge the air into the plenum; and - an air heater (322, 214) configured to heat at least some of the air in the plenum prior to a portion of the air entering the cooking chamber from the plenum via air delivery orifices; wherein the chamber outlet port comprises outlet perforations combining to form a first geometric shape centered on an axis of the airflow generator, wherein the air delivery orifices comprise a first set of inlet perforations disposed near the top of the cooking chamber and a second set of inlet perforations disposed near the bottom of the cooking chamber, which sets each form strips of perforations, the first and second sets of inlet perforations (350, 355) combining to form respective second and third geometric shapes that are disposed on opposite sides of the outlet perforations, and wherein the second and third geometric shapes are different than the first geometric shape, characterized in that the strips of perforations (350, 355) are formed from individual rows of perforations that extend linearly along a direction substantially parallel to the plane in which the top or bottom of the cooking chamber lies, that the number of rows of perforations that form the second set of inlet perforations is larger than the number of rows that form the first set of perforations, and that the center of the outlet perforations is closer to the second set of inlet perforations than the first set of inlet perforations.