The present invention provides a barbecue grill assembly comprising a cooking chamber with a cover and a firebox. The cover is moveable between an open position and a closed position. The cover has an inner surface and an internal lip extending from a lower edge region of the inner surface. The firebox has a rim at an upper portion of the firebox wherein the rim defines a periphery of the firebox. When the cover is in the closed position, the internal lip is positioned inward of the firebox periphery. This means that the internal lip is positioned within the perimeter of the firebox, as defined by the rim. The grill assembly further comprises a burner element positioned in the firebox, a cooking grate positioned in the firebox above the burner element, and a frame assembly adapted to support the cooking chamber.