Three baking trays will take longer to bake than one. Seven minutes longer for your cookies seems about right. I always bake cookies one sheet at a time. Depending on the cookie, I may need to add 2 or 3 minutes per tray. Not always though.

Do you have an oven thermometer to test the temperature? When I got my oven, it didn't seem to be as hot as it should, so I tested it. It was a few degrees off. There should be instructions with your manual on how to reset it to the correct temp. Mine really wasn't off that much, but I my previous stove was ancient & the oven was always really hot. I had learned to adapt the temps, so when I got one that worked it took me quite a while to get used to it.

Preheat. My new oven beeped in about 7 mins to tell me my oven was preheated to the temp I put it at. But it wasnt even close to the desired temp yet.

I had a technician tell me to always preheat the oven for 30 mins.

That bothers me if I'm baking something that only has to bake for 10 mins - to preheat 30 mins?

Were you baking convection or regular?
What kind of cookie sheets were you using? Do they cover the whole rack?
Pre-heating the oven is important, opening and closing the door will cause heat lose and the cookies my bake unevenly and/or take longer to cook.
I've know some people to pre-heat with a pizza stone on the bottom rack once the stone is pre-heated it helps regulate the oven temp.

shirleywny5 - The thought of having to bake one cookie sheet at a time, especially around Christmas time when I do lots and lots of baking, makes me almost want to cry LOL

Shaun - I pre-heated my oven and besides taking forever to beep when it reached the desired temp, when I tested the temp with an oven thermometer is still wasn't fully pre-heated. I don't know why it takes so long.

lisacdm - I was baking regular (not convection) and using baking sheets from the Pampered Chef. They are large but do not cover the whole rack. I set my timer for 15 min and did not open the oven until the timer went off. At that point I just turned the oven light on and kept an eye on them to see when they looked done so I did not have to keep opening the oven.

Unfortunately, it is not just cookies. A tray of brownies took forever and still weren't cooked right.

I make cheesecake every year at Christmas which is supposed to bake for an hour and then remain in the oven for an additional 2 hours and I can not open the oven at all during this time. I am super nervous because I do not know how to judge the cooking time.

I am beginning to think I should have just kept my old horrible oven - at least I knew what I was dealing with LOL

Thanks for the input.

Wish I could help - boy Electrolux has really been hitting the tv airwaves with their ads on their new high-end kitchen appliances. They look great in the ads. Have you called them?

My sister has the new Electrolux cookstove that does everything and loves it. I know it has been quite an experience for her just trying to figure out all it will do.

We had a college graduation party for my daughter Saturday night at her house. We had 10 pans of appetizers that cooked at 350 for 20 minutes and they were all fine. Cooked perfectly.

I just wander if your oven temperature is off. I would check that first

Ditto on the oven thermometer. That will tell you in a jiffy how accurate your oven is, and will make your cooking efforts more reproducible.

I have an ancient gas oven which is off a bit, but I just know from experience (having used the thermometer as a reference) to add about 25 degrees across the spectrum, and it'll work out fine. (That is, if the recipe calls for 375, I'll put the dial at 400 and it delivers 375.)

You don't have to spend a lot; you can get a good one for about 12 or 15 dollars.

I did buy an oven thermometer but I do not think it is accurate. I had my mother test it and the temp was off in her oven as well. Can anyone recommend a particular oven thermometer. I just made one tray of the pre-sliced Pillsbury holiday cookies. It should have only taken 8-10 min but it took 17 min.

Cooks Illustrated liked the one at the link, and that's the one I use.

Some of the reviews at Amazon are negative, but I have to say that this item has worked just fine for me. I guess there are sample to sample variations accounting for different responses to it.

Here is a link that might be useful: Taylor thermometer

You say Pampered Chef baking sheets...the stoneware right???
The first batch will take as much as 5-7 minutes more than any other..the stone has to warm up...And putting in 3 baking stones is alot of work for an oven to keep the temp and heat those stones.
I bake on Pampered chef stones all the time..they are MY COOKIE SHEETS..but never more than 2 pans at a time, and they must be rotated, because the upper pan will keep the lower pan from browning and the lower pan will keep the bottoms of the upper pan for browning properly.
So..if you are using stoneware, I'm sorry but drop it down to only 2 pans at a time..and rotate halfway through.
It's not necessarily your oven on this one.. :o)

arley - thanks for the recommendation.

terri pacnw - Not the stoneware. I have those as well but Pampered Chef also has baking sheets. They are pretty heavy so maybe that is the problem. I have a tech coming tomorrow to look at my freezer so I will have him/her take a look at the oven.

oooh, didn't realize they'd added baking sheets...I haven't looked at current product line up in years.. :O) I had to avoid the temptation of my bad habit..LOL