The Campain-oven is a portable Oven made of red Copper, three or four Inches high, of a convenient length, and raised a little upon Feet, so that a Fire may be kindled underneath, as occasion requires: The Cover or Lid of it ought to have Ledges, to hold Fire likewise, when it is necessary to put some on the top, or on both sides: This Cover must be taken off from time to time, to see whether that which is contain'd in the Oven be sufficiently bak'd or brought to a good Colour. For want of such an Instrument, the Kitchen-oven of Masons-work, or some other may be us'd, accordingly as a convenient opportunity may be found; or else a Silver-dish and certain large Baking-pans that are order'd almost in the same manner.
The Court & Country Cook, Massialot. 1702, p. 9 [New Instructions for Confectioners].
Some tourtières were lined with tin and could be used as a baking pan itself. Others were not lined and were used with an inserted baking pan of ceramic or metal.These little ovens could be used in the fireplace off to the side with some coals both under and on top to control the cooking temperature and even browning of the item inside. They would work equally as well in a campfire setting.