An improved tray ration heating system includes a reservoir. A heat exchanger transfers heat to the reservoir. A firebox at one end of the reservoir has an opening to receive a burner flame tube. The firebox delivers heated gases from the burner flame tube along the underside of the reservoir to an opposite end of the reservoir. A main channel along the reservoir includes baffles which produce a tortuous path and introduce turbulence to, the hot gases. First and second channels adjacent to the main channel redirect hot gases exiting the main channel, and third and fourth channels direct hot gases exiting the first and second channels towards the opposite end of the reservoir. An exhaust channel extends along a vertical wall of the reservoir to an exhaust opening. The exhaust channel has baffles for displacing hot gases across the vertical wall. An insulated outer liner supports the reservoir and heat exchanger.