Brewing Oven, also known as an OAST, is a type of oven used in the brewing process. It is used to dry hops and other ingredients before they are added to the beer. The OAST is usually made of brick or stone and is heated by a fire. The heat from the fire is then circulated through the oven, drying the ingredients. The OAST is an essential part of the brewing process, as it helps to create the desired flavor and aroma of the beer.