You make all of these with similar ingredients, but a crustless quiche is often made with more milk or cream and has a delicate texture. A frittata can be made on the stovetop or in the oven and is usually made of eggs, a little milk and filling. It also usually has a firmer texture than a quiche or omelette. An omelette is cooked quickly in a pan and is usually made of just eggs and filling.