Ovens often take longer to stabilize to a gvien temperature even though it may beep. As long as the oven keeps heating up to the temperature you set it for and stabilizes there, you're probably fine.

The oven on my new Kenmore induction range does the same thing. Just about the same timing. You need to retrain yourself and get a good oven thermometer. Not what you wanted to hear .... anyway, I think these energy saving appliances are a royal pain in the ying.

Oh no -- I'm back to using an oven thermometer? After spending $1,400? You're right, not what I wanted to hear. the thing is, though, the oven sometimes does and sometimes does not eventually get to the right temperature. The repair person is coming tomorrow afternoon. I'll let you know what he says.

thanks!

The tech should be able to tell you there's nothing wrong with your oven.

The electronics that they are building into ovens these days is very sophisticated. When a heater element is on and hot it stays hot for a while even after the power is turned off to the element. In other words the element doesn't get instantly cold the moment power is shut off.
If an oven keeps the element turned on until the set temperature is achived the oven will actually continue to heat until the element cools enough to let the temperature stabilize. This will be higher than your set temp.
These new ovens recognize the heat carry over of an element and shut it off before the set temperature is achived. The oven temp continues to rise then stabilizes more closely to the temperature you set it for.

Customers who don't use a thermometer never notice a difference and just see the oven baking perfectly.

Another thing to note is if you are using a Bi-Metal oven thermometer (the most common type)these are very slow to react to temperature change and tend to lag several minutes behind the actual temperature.
For my service work I use a digital thermometer with thermocouple sensors. These have very fast reaction times and tend to read the actual temperature while the bi-metal thermometer is still 50º behind.

Thank you, jakvis. (That must be why the fan runs for such a long time after i turn the oven off.)

This user did notice a difference, though, because the cookies weren't baking. So: if the digital display reads 350 when the oven is, say, at 250 or 275, how do I know when to put the cake in? Is there no way for the display to recognize when the real 350 is reached? Ten or 15 minutes at a wrong temperature can ruin a delicate cake. (I'm a serious baker.) Thanks awfully for any advice! I guess I might have to get a digital thermometer.

If your a serious baker you should allow the oven to settle into it's temperature before putting a delicate bake goods item in.
When you use the preheat on an oven it basically is telling you that the air around the sensor is at the temperature you selected. The problem is the mass of metal and glass is not at the temperature you selected. For most baking this is fine.
I do service work for a couple people who enter a lot of contests and they always tell me that they let their oven heat for 45 minutes to an hour before putting their bake goods in the oven. This is to make sure that everything in the oven, door, glass, walls, insulation, has heated and settled to the set temperature.
I recently received some info from Bosch on the best settings for different food types with their new oven. You might want to call them and have them email you the pdf's.

Jakvis- Is the digital thermometer with thermocouple sensors expensive? I had to have my double wall ovens calibrated after a repair and the tech would only test the temperature on regular bake. The manufacturer said the tech should have checked the temp on other settings- like convection bake. Would you be willing to offer your opinion on purchasing a thermometer like you use?

The digital Thermometer I use is a UEi that I think I paid around $150 for. but it's overkill for a consumer.
As far as retesting what your service tech already tested I don't think it's neccessary. The PTC sensor in the oven works the same in all cooking modes so it really doesn't know what mode you selected. It's just a resistor that changes value when heated or cooled. The electronics read the resistance value to determine what the temperature around the sensor is. Sooo, if the temperature is set for 350º and the sensor reads 350º in bake it will read at the same value for convection bake, convection roast, etc.

jakvis - your answer makes sense. thanks for the information.

Jakvis: one last question -- the oven seems not to get the bottoms of cookies and other baked goods done enough. Do you think it has to do with the hidden heat element? Could something be wrong? Or should I just leave them in 5 or 10 mins. longer? Thanks.