Baking vs. cooking usually means just one thing: One is more precise than the other. When it comes to making homemade breads and pastries, it's important to follow recipes precisely all the way down to the temperature of the oven and how long you preheat it before baking. But when it comes to cooking entrees and meals in the oven (think casseroles, pizza and baked mac and cheese), preheating the oven is not necessary. So skip wasting all that energy by preheating and start cooking right away. You can ignore the preheating tip in cookbooks to save energy and time the next time you cook.