Hello LauraS! A range or wall oven with all racks in the oven cavity will preheat to 350°F in: 12 - 15 minutes (+/- 5 minutes). If you are still having issues, we would recommend contacting KitchenAid® at 1(800)422-1230. We are available weekdays, between 8 am to 8 pm EST. They will be better able to assist you.