Two different dishes can bake at the same time when their temperature difference is 20°C / 36°F or less. Choose a midpoint temperature and track each cooking time separately. The convection setting makes this easier. However, foods with strong odors should not bake alongside desserts, and the fuller the oven, the longer both dishes take.
The first question is temperature. If the difference between the two recipes is no more than 20°C / 36°F, choose a temperature between them so the two recipes can bake together. A savory pastry that calls for 180°C / 355°F and vegetables that call for 200°C / 390°F can bake together at 190°C / 375°F. The dish baking at the lower temperature will take a little longer, while the one baking at the higher temperature will take a little less time. If the temperature difference is greater than 20°C / 36°F, bake the dishes one after the other; putting a cake and a pizza in the oven together can ruin 2 dishes. Reassess the cooking times when you choose a shared temperature. Grouping dishes that bake at the same temperature is the most practical approach.
The second question is time. The two dishes often have different cooking times, so put the one that takes longer in the oven first and add the quicker-cooking one later. Opening the door to add it lowers the oven temperature, and the oven takes a few minutes to recover, so extend the cooking time a little to account for that. Check each dish separately. Instead of trying to remember the times, set two separate timers; that is the most practical approach when you are preparing a large meal. Write down the order so you do not get confused in a busy kitchen.
The third question is odor. The smells from fish, garlic, onions, and pickled foods spread with the moisture in the oven and transfer to desserts, cakes, or milk puddings baking in the same space. For this reason, foods with strong odors should not bake alongside desserts. A covered dish or an oven bag reduces the spread of odors. The same rule applies to an air fryer. After cooking something aromatic, you can heat the empty oven for a few minutes and air it out. Grease that builds up on the oven glass also holds odors for a long time.
The fourth question is placement. Arrange the trays diagonally rather than directly above one another, leave at least 2 to 3 centimeters of space between them, and make sure neither touches the oven wall or fan. Food on the upper rack browns more on top, so place the dish that needs a browned top above and the one that needs a crisp bottom below. Switch the trays halfway through cooking. The convection setting is preferred for the 2 dishes because it reduces differences between the racks. Keep the door open only briefly while switching the trays.
The final question is capacity. The fuller the oven, the longer it takes to recover its heat, and the 2 dishes may take longer than expected, throwing off the time estimates. If the combined volume of the 2 dishes exceeds what the oven can comfortably hold, baking them one after the other may finish sooner. Keep the first dish warm at 70–90°C / 160–195°F or in a covered dish. During this wait, keep fried and crispy foods uncovered on a wire rack so their crusts do not soften. Baking in sequence often takes less effort and gives better results.