This term refers to both a baking dish and the ingredients it contains. Casserole cookery is convenient because the ingredients are cooked and served in the same dish. A "casserole dish" usually refers to a deep, round, ovenproof container with handles and a tight-fitting lid. It can be glass, metal, ceramic or any other heatproof material. A casserole's ingredients can include meat, vegetables, beans, rice and anything else the cook desires. Often a topping such as cheese or breadcrumbs is added for texture and flavor.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.