It’s not always necessary to preheat toaster ovens, though it’s important to know when it is and isn’t going to affect your food. Generally, preheat your oven when cooking at high temperatures, and want to create a crispy, browned texture. This will ensure your food is always being cooked at the maximum heat. On the other hand, if you’re just quick-heating some food or cooking a dish where browning isn’t a concern, feel free to pop it in as soon as your toaster oven begins to heat.