Cooking is more an art than a science; oven temperatures are recommendations rather than rules, and can be adjusted within certain parameters for your own cooking needs. If you want to cook several dishes together to save time and energy, it's certainly possible. Once your meal repertoire includes foods that cook at roughly the same time, you can mix and match entrees, side dishes and desserts however you wish.
Oven Temperature Variations
Your oven's temperature is not precisely what it says on the oven knob. Not only do all ovens have some variation in temperatures, but those variations are not critical to the success of many foods. You do need precision when making cheese puffs or browning a pie crust, but for foods such as casseroles or baked potatoes, variations of as much as 25 degrees F won't affect the food.
Casseroles, Roasts and Cookies
Casseroles, from lasagna to chicken and rice, typically cook at 350 degrees F for about 45 minutes. Opening the oven door every 10 minutes to add or remove a rack of cookies won't hurt the casserole. Pork loin roasts can be cooked in the oven at 350 degrees F for 25 minutes per pound, or until they reach 170 degree F on a meat thermometer; adding a rack of cookies above the roast will allow you to bake several batches of cookies and not interfere with the roasting process. If you've got room, place vegetables around the perimeter of the roasting pan and roast them during the last hour of cooking, for a complete meal.
Fish and Bar Cookies
Cooking bar cookies in an 8-by-8-inch pan gives you plenty of room in your oven to place an 8-by 11-inch pan containing fish. Cut into individual serving pieces, fish fillets cook in a 350 degree F oven -- the same temperature that works well for cookies -- for about 20 minutes. Begin cooking the cookies before adding the fish to the oven if they take longer than 20 minutes to cook.
Baked Potatoes and Apple Cake
A baked potato with cheese, salsa, chili beans or scallions makes a delicious vegetarian main course, and can be baked in an oven at 350 degrees F. An apple cake with grated apples and lots of chopped walnuts for protein also takes a 350 degree F oven. Both the cake and a medium-size baked potato cook in about 50 to 55 minutes, so they can be done at the same time without any adjustments in time.