It Is Not Necessary to Always Preheat the Oven
We all preheat the oven without thinking, but in many cases this step can be eliminated, saving a little time and energy.
As Epicurious explains, preheating the oven before placing food in it is only necessary for foods that need to be heated immediately to a certain level of heat in order for them to work:
Take bread, for example: here the high temperature of the oven provides the last little push the yeast needs to raise the dough to the highest possible height before the flour structure sets; Starting in a cold oven creates a flat, dry, chewy product. A similar principle is true for doughs or batter fermented with baking soda and / or baking powder – for example, cakes and cookies – that also need a certain level of heat applied quickly to get the job done.
Usually, if it contains flour and / or eggs, preheat the oven. If it doesn’t, you can put whatever you do in there as soon as you start that child. Casseroles, stir-fries, and vegetable trays all fall into this category, so feel free to toss them when you’re ready, whether the oven is fully heated or not.