Preheat Baking Sheets In The Oven For Quick And Even Cooking
If there is one piece of advice that even the most inexperienced home cook knows, it's to preheat the oven before use. But far fewer people know the benefits of preheating a baking sheet. Keep in mind that this is a tip for cooking, not baking (more on that in a bit), and give this method a shot — you'll find that a preheated sheet will take roasted vegetables and meats to a more flavorful place.
Preheating the sheet pan is a timesaver because the food will start roasting right away on a hot pan, which reduces the overall cooking time. The food is also more evenly cooked because it heats on all sides from the minute it hits the oven, instead of the top surfaces of the food getting the oven's heat while the bottom surfaces rest on a baking sheet that hasn't yet come up to oven temperature. In addition, preheating the sheet helps mitigate the effects of hot spots in the oven that cause uneven cooking.
Best of all, however, is how the texture and flavor of roasted meats and vegetables improves. Without preheating the baking sheet, ingredients that contain a lot of moisture will essentially start to steam in their own juices before they roast, softening and never quite developing that crispy exterior you want. But start the process on an already hot pan, and moisture in the food evaporates quickly, resulting in better browning and caramelization.
Great for fries but not for cookies
To try out this tip, simply place an empty, untreated baking sheet inside the oven to preheat both at the same time. It's okay to line the sheet with aluminum foil first, to cut down on cleanup after cooking. However, you should not use parchment paper, which doesn't allow optimal browning and caramelization. Prep your ingredients as usual, tossing lightly in oil and seasonings as desired, then add to the baking sheet once it is hot.
Do keep in mind that although preheating is ideal for veggies and meats, heating your baking sheet before baking is not recommended. Cookies, for example, will stick when added to a hot surface, and any dough containing butter will spread. Baking also requires more precise control of exact time and temperatures for it all to come together, so while preheating the oven is advised, a cold baking sheet is called for.