As shown in the top image this pit technique can be used on a very large scale! However the principle is the same as demonstrated below using just a Dutch oven.
Although there are several other ways to pit barbecue, the Dutch oven technique is illustrated here, as it provides the most versatility for camping purposes. Almost anything that can be cooked in a Dutch oven can be cooked this way.
A pit barbecue is an exercise in turning a hole in the ground into an oven. Of course, coals provide the heat. Covering the top with tin, then dirt, regulates the oxygen so the coals burn slowly, providing an even, controlled heat for many hours (8-12 ).
The really great benefit of this procedure is that the evening meal can be prepared and put in the ground first thing in the morning. Then it will be ready when you return later that night, perhaps exhausted from the days activities . Thus, you have a meal prepared and the work is already done!
For most meals just cover the bottom of the oven with quartered onions, then put your main course meat on top of that with carrots, potatoes etc.. around the sides. Roasts, ham, turkey, chicken and Cornish game hens are all wonderful cooked this way but you can also do beans and stews. Also often there are enough coals to do some biscuits or a Dutch oven cobbler or maybe just cook a frozen pie after the main course has come out of the hole.
The hole can be reused many times by just digging out any unburned coals (put them in your main fire ring). When done camping fill the hole with dirt and mark or note where the opening is so you can easily find it the next time you camp at that spot. That way, digging the hole is very easy the next time.
It may take a little practice to get the hang of this cooking method but it is well worth learning. The two main tricks are use lots of water and make sure there is no smoke once things are covered.