&nbsp Harold McGee, author of The Curious Cook, had the same question you do. He says he used to work as fast as possible to avoid losing oven heat, and that his haste "resulted in misadventures more than once." So he determined to find the answer to this age-old burning question.

His measurements showed that you might lose 100°F (38°C) or more if you hold the oven door open for one minute when the oven is set at 350°F (175°C) or higher. But what was surprising was that the temperature bounced right back within a minute of closing the door. He says he performed the test with a gas oven and that the temperature usually rebounded without the burner coming on, speculating that the residual heat in the oven cavity was enough to reheat the air inside the oven so quickly.

McGee admits that other ovens may not respond exactly as his did, but, he says, "I'll bet that most cooks can afford to relax."