A field-ready oven has reinforced telescoped side walls that extend and hold a base, shelf, tray support and cover spaced apart. A low air intake and a semipermeable membrane deliver air and vapor fuel to catalyst pads on the shelf. Radiant heat from exothermic reaction is diffused over a bottom of a tray. Hot gas circulates around the diffuser and tray with a chimney effect before exhausting. A lid on the cover lifts for access to the tray. A fuel container in the oven forces fuel through a capillary restriction to limit fuel flow. A spring in the container is released to start fuel flow.