Using Too Many Pans in the Oven
So, you decided to cook for an army, but, you only have one oven. It may be tempting to simply put a bunch of pans or cookie sheets in the oven all at once, but this can actually keep everything from cooking properly. The more you put in the oven, the less the heat will circulate, which not only will give you undercooked food, it can change your recipe.
Overloading will reduce the airflow in the oven dramatically. If you want to bake up several batches of your recipe, it is best to stick to two sheets or pans in the oven at a time. Just wake up extra early so you can get a head start on your baking plans and leave the overloading to the gym rats.