Cooking your food for the recommended time without first preheating your oven can result in undercooked or soggy food. It’s therefore important to preheat your oven every time it is used. When you first turn your oven on it will be cold, and will take time to reach the required temperature. The hotter the temperature, the longer it will take the oven to reach it. Preheating your oven involves setting the temperature and leaving your oven to achieve this before placing your food inside.