if u want the most consistant temp, u need to let it preheat for 20 to 30 mins, this preheats the inner liner, racks, etc, and eventually stabalizes oven temp and the overswings are less harsh, yes, every home oven does have a temp over swing, when calibrating an oven, u calibrate the average temp... some ovens have tremendous 100F overswings, while others have 30-50F overswing, and then the speed at which it swings will be reduced greatly with good preheat... anything that bakes at or under 15mins is considered delicate baking and preheat is required for proper baking results, also consider the color of your pan if this is an electric oven, the darker the pan, the hotter its surface area, but if after preheating for 30 mins, insert items in oven when the heating indicator light turns off, this means that u will be above the set temp, when u open the door, temp will drop maybe 30 degrees or so, and this will put the actuall oven temp closest to the set temp for around the 4-5 mins... VAPE ON!