An oven for preheating glass containers in which the containers are moved through the oven on a conveyor with the conveyor moving at a linear speed that is in excess of the permitted speed of the container movement. This permits the containers to produce a "gear effect" rotation of the containers that are guided on the conveyor by side rails that are spaced apart a distance greater than the container diameter. A source of heated air is directed against the shoulder of the container by an adjustable nozzle and another nozzle is directed against the heel so that these areas of the container will be preheated so that the shrinking of a plastic label about the container will be uniform.