Abstract: An apparatus for converting a barbecue into a pizza cooking oven includes an open door frame and vertical side panels pivotally attached to the vertical side posts of the open door frame. The side panels can be pivotally adjusted on the open door frame to extend rearward of the open door frame at different pivot positions. When the side panels are extended rearward of the open door frame, the bottom edges of the side panels provide a support base for setting the apparatus onto the top rim of a bottom bowl of a barbecue and the top edges of the side panels support a cover of a barbecue in an elevated position above the bottom bowl of the barbecue. The elevation of the cover creates an expanded cooking chamber above the bottom bowl of the barbecue and the open door frame provides access to the expanded cooking chamber.