After you've loving mixed your dough, scooped up balls and evenly placed them, you want your cookies to come out perfectly. But you also want to save time. Can you bake two trays at a time? Baking multiple trays does not affect the cooking time, but you do have to make other adjustments.
Baking One Tray
Many experts suggest that baking one cookie sheet at a time is ideal. This allows for even heat circulation around the sheet, ensuring that each cookie will be browned the right amount. It also allows the cookie tray to be placed in the center of the oven, so that it is not too close or too far from the heating element.
Baking Two Trays
If time is of the essence, it is certainly possible to make two trays of cookies at a time. Unlike in a microwave, putting more food in an oven does not take it longer to cook. However since the heat in an oven comes from one source, areas of the oven may cook unevenly. When baking two sheets at a time, you should rotate them -- both front to back and switching shelves -- halfway through the baking time.
Baking Multiple Trays
Baking two trays of cookies at a time is fairly standard, but if your oven has space for more, three or four can be used. Industrial ovens often have five or six racks. Putting four trays of cookies in an oven will still not affect the cooking time, but the trays may still need to be rotated for even browning.
The baking time of your cookies will be the same whether you bake one tray or four trays -- assuming your oven is large enough to handle them. Oven racks should be evenly spaced and at least several inches away from the heating element. Most importantly, know your oven. After using it several times, you will better know how things cook and what areas of the oven are hotter.