What is a bialy? It is often referred to as "the bagel's cousin". And to anyone who has ever had a bialy, you'll know that it's true. A bialy is just about the same size as an average bagel, but the bialy is flatter and lighter than a bagel. Unlike a proper bagel it is not boiled. A bialy has a depressed center, not a hole. The depression is typically filled with tart diced onions or a garlic/poppy seed blend.