We've all heard that a quick look in drops the temperature, but Warner points out just how damaging such a move can be to a time-pressed cook: Every time you pull that door down, you're lowering the oven temperature by at least 25 degrees, and it can take five or even 10 minutes to return to the initial level. That translates to up to 20 extra minutes for a roast chicken if you open the oven just twice during the cooking. Warner has two solutions for curious cooks: First, keep the window clean so you can observe the color of whatever you're cooking from outside. Second, get a probe thermometer, such as the CDN Dual Sensing Probe Thermometer and Timer
($30), in which one end of a cable holds the actual thermometer, and the other end (which you keep out of the oven) has a display with the temperature. Some even have meat selector settings so you can tell, for instance, when beef is medium rare.