Oat Bran - The outer casing of the oat, often used as a high-fiber nutrient supplement. Thought to fight against high cholesterol, oat bran is high in vitamin B-1 and contains a good amount of vitamins B-2 and E. It is available in health-food stores and some supermarkets.

Oatmeal - Oats that have been cleaned, toasted, hulled and cleaned again; most often cooked and served as cereal. There are several varieties of oatmeal. Old-fashioned oats (also called regular rolled oats) have been steamed and flattened by huge rollers and take about 15 minutes to cook. The quick-cooking variety of rolled oats (they cook in about five minutes) are groats that have been cut into pieces before being steamed and rolled into thinner flakes.

O'Brien Potatoes - A dish of diced potatoes, onions, and sweet peppers or pimientos, fried until browned and crisp.

Oeuf - The French word for "egg."

Okra - A vegetable brought to the U.S. South by African slaves. Okra pods are green and ridged. When cooked, okra gives off a viscous substance which may serve as a thickener in some dishes.

Olive - The small fruit of a tree native to the Mediterranean region; has a single pit, high oil content, green color before ripening and green or black color after ripening and an inedibly bitter flavor when raw; eaten on its own after washing, soaking and pickling, or pressed for oil; available in a range of sizes (from smallest to largest): medium, colossal, supercolossal and jumbo.

Olive Oil - An oil obtained by pressing tree-ripened olives; has a distinctive fruity, olive flavor and is graded according to its degree of acidity; used as a cooking medium, flavoring and ingredient.

Omega-3 Oils - A classification of fatty acids found in some plants and in all sea creatures; found to be beneficial to coronary health (purportedly lowering the bad LDL cholesterol and raising the good HDL) as well as to brain growth and development.

Omelet - Seasoned eggs that are beaten and fried. The eggs will puff up at which time, they are rolled or folded over.

Omelet Pan - A shallow pan with sloping sides, a flat bottom and long handle.

Onion - Bulb vegetables related to the lily, with a characteristic strong flavor and odor.

On the Half Shell - This phrase usually describes oysters served on the bottom shell, either raw on a bed of crushed ice or cooked on a bed of rock salt.

Open-faced - A sandwich prepared with just one piece of bread and topped with a wide variety of meats, vegetables or cheeses; the sandwich can be served hot or cold.

Orange - Any of a variety of citrus (Citrus sinensis) with juicy, orange-colored segmented flesh, a thin to moderately thick orange-colored rind and a flavor ranging from bitter to tart to sweet; depending on the variety, an orange can be eaten fresh, cooked in sweet or savory dishes, juiced or used as a flavoring or aromatic.

Orange Roughy - A mild flavored New Zealand fish with white flesh, orange roughy is also low in fat.

Oregano - An herb (Origanum vulgare) and the wild form of marjoram; has a woody stalk with clumps of tiny, dark green leaves that have a pungent, peppery flavor and are used fresh or dried, principally in Italian and Greek cuisines; also known as wild marjoram.

Organic Food - Food grown without the use of any chemicals, including synthetic fertilizers, pesticides or fungicides. No artificial coloring or flavoring or other additives can be used in processing foods labeled organic. Specifics vary from state to state.

Orgeat Syrup - A sweet syrup used in cocktails, orgeat syrup is made with almonds, sugar, and rose water or orange-flower water.

Orrechietti - Pasta shaped by pressing the point of a knife into a small slice of dough, resulting in a shape similar to a small ear.

Orzo - Italian for barley and used to describe rice-like pasta.

Ouzo - A clear anise-flavored liqueur from Greece.

Oven Bag - A heat-resistant nylon bag for cooking meals without basting or tending.

Oxalic Acid - Oxalic acid is found naturally in many plants, but is poisonous in excessive amounts. Spinach, rhubarb, sorrel all contain measurable amounts of oxalic acid. It actually forms insoluble compounds with calcium and iron which inhibit their absorption by the human body, thus diminishing the purported nutritional value of some vegetables, particularly spinach.

Oyster - Bivalve mollusks with a hard, rough gray shell and creamy-beige to pale-gray meat.

Oyster Mushroom - A smooth-capped mushroom with a fan shape and mild oyster-like flavor. They're found dried or fresh in many supermarkets and most oriental markets.

Oyster Sauce - A bottled all-purpose Chinese seasoning made from oysters, water, salt,cornstarch, and caramel coloring.

Oysters Rockefeller - This creation was born in New Orleans in the late 1890s, and was reportedly named for John D. Rockefeller because of how rich it is. The dish is composed of oysters on the half-shell baked with a mixture of spinach, shallots and celery then topped with bread crumbs.