Pastries, pies, vegetables and roasts can be cooked in a convection oven, but almost any food suitable for baking or roasting can be used. Cookies and breads are exceptions, as they may dry out too quickly in a convection oven, but adjusting the temperature may solve this problem.
Standard ovens use heating elements in the top and bottom of the oven cavity. Convection ovens use these elements as well but also use fans to circulate heated air in the oven cavity. This provides more even heating of all food surfaces, resulting in faster and more even cooking. In good-quality models, the fan is paired with a third heating element that heats the air drawn in by the fan, eliminating the problem of having hot and cold spots in the oven.
Cooks may need to make a few adjustments when using a convection oven. Using pans with low sides allows the heated air to circulate freely around the food. Convection ovens typically reduce normal cooking times by about 20 percent, so check foods after about three-quarters of the time recommended for conventional cooking. Cookies, breads and cakes may require the temperature to be lowered by 20 to 25 degrees from recommendations for conventional ovens to ensure that they don't dry out before they have had time to rise properly.