1 If you have an older oven, you may not have a dial with the different temperatures written on it; you may just have an on-off switch. If this is the case, simply turn on the oven and wait 10 to 15 minutes before setting the items to be baked inside.  Consider using an oven thermometer.
http://www.wikihow.com/Preheat-an-Oven
Re: how long do you preheat oven as stated in recipies. You should preheat it until it has reached your desired temperature. My oven turns off a light at that point. If your oven cant tell you, you could use a oven thermomether.
http://www.jamieoliver.com/forum/viewtopic.php?id=39877
How will I know if for example I need to preheat my toaster oven to 350 degrees? It depends on what you are using the toaster oven for. If you are reheating food then you won’t need to preheat it, but any type of cooking will work best if you preheat first. The reason for this has to do with the cooking time.
http://amysayscook.com/preheating-a-toaster-oven
Re: how long do you preheat oven as stated in recipies. kathy, I recommend you try an oven thermometer, I was astounded the first time I did, what it revealed about my oven is that it needs a long time to heat and it takes forever to recover from having the door open. All ovens are so different.
http://www.jamieoliver.com/forum/viewtopic.php?id=39877
How long do you preheat the oven for. I don’t really preheat my toaster oven anymore. Instead, I adjust the cooking time by shortening it, then I put food directly in as soon as I start it. Preheating varies from machine to machine, so it’s hard for me to recommend a specific period of time.
http://amysayscook.com/preheating-a-toaster-oven
This light is usually next to the oven temperature dial. 1  Most ovens take 10 to 15 minutes to heat up to the right temperature.  If you have an older oven, you may not have a dial with the different temperatures written on it; you may just have an on-off switch.
http://www.wikihow.com/Preheat-an-Oven
Three Methods:Preheating an Electric OvenPreheating a Gas OvenPreheating an Oven at a High-AltitudeCommunity Q&A. Before you bake something, your oven needs to be heated to the proper temperature. While it takes only a few seconds to turn on your oven, it can take several minutes for it to reach the right temperature.
http://www.wikihow.com/Preheat-an-Oven
The average time to preheat an oven to 350° is about 15 minutes, but the time varies depending on the stove. Older stoves may take longer to preheat; some newer stove models have a fast preheat feature. If you're preheating to 450°, add another five minutes to the time. The only way to figure out how long it takes your oven to preheat is by testing it with an oven thermometer. Place the thermometer in the center of a rack set in the middle of the oven, then turn the oven to 350°. Set an oven timer, then check the temperature on the thermometer at 10 minutes, then again at 15 minutes.
https://www.thenest.com/content/cooking-qa-preheating-the-oven
Re: how long do you preheat oven as stated in recipies. Normally about ten minutes. Some recipes instruct you to turn the oven on before you even start, and I sometimes find this excessive. It should be ok for meat, but for a pie, for example, I turn the oven on when the pastry's ready for rolling out.
http://www.jamieoliver.com/forum/viewtopic.php?id=39877
1 Most ovens take 10 to 15 minutes to heat up to the right temperature.  If you have an older oven, you may not have a dial with the different temperatures written on it; you may just have an on-off switch. If this is the case, simply turn on the oven and wait 10 to 15 minutes before setting the items to be baked inside.
http://www.wikihow.com/Preheat-an-Oven
how long do you preheat an oven
It takes 10 to 15 minutes to preheat an oven. Preheat an oven for 10 to 15 minutes.