Bowls are a ubiquitous part of medieval dining. Typically they would be made of wood or pottery although other materials such as pewter, silver or gold were available for the better off.
Care should be noted as to the form of the bowl as they do vary throughout history in their shapes.
Bowls in the SCA
Wooden or ceramic bowls are ideal for SCA events. You can purchase them for 50c - $3 from any local op-shop if you don't have one at home.