I'm cooking a turkey for thanksgiving for the first time. I've got a beautiful 11 lb turkey and according to the websites I found, I should cook it for about three hours. When I asked my girlfriend's experienced cook mother though, she said that time was really low. Just looking for a second opinion.
The best way to know if your bird is done is by checking the temperature of the thigh with a probe thermometer. You're looking for about 160 F. If you don't have a probe thermometer, and you're cooking a turkey, this might be the time to invest in one.
It really depends on the preparation. For example, a brined, pre-thawed turkey would talk less time.
Traditionally, the rule of thumb is 15 minutes per pound and then you start check for mobility in the drumsticks (that indicates it's done). It also takes longer if you've packed the turkey with stuffing/vegetables/etc.
Since it's your first turkey, I'm not going to tell you to go against a mother, but...
I use the high heat method. I have already brined the turkey (if you haven't and have some time, soak the turkey in salty water, 1 Cup/gallon of water for 3-4 hours) but that isn't what makes it zip by.
Crank the oven to 400. Put the turkey in a roasting pan on a V rack, back and legs up (it looks upside down, from all the perfect pictures on magazine covers). Roast for 30 minutes. Pull it out, flip it over (be careful, it's hot), rub with butter to help it brown and then put it back in the oven for 50-60 minutes. Start checking it with a quick read thermometer at 50 minutes. You are looking for 165 in the breast meat, 170 in the thighs.
Pull it out, put on the cutting board and/or platter, cover with foil and LET IT SIT FOR 30 MINUTES. Or more. Don't carve a turkey when it first comes out of the oven. That is true no matter how you roast it.
I started cooking turkey using the high heat method about 5 or 6 years ago. It drives my wife crazy because it takes me a couple of hours to have a perfect turkey, whereas when she used to do the cooking "like her mother taught" it took all day.
I was always told 20 mins / pound + 20 mins. That works out at closer to 4 hours than 3, I think. If you stuff it before you cook it then add time on.
Also, something that someone told me recently was that the stuffing should be cold when you stuff the raw Turkey (to prevent it cooking and re-cooking). I've cooked Turkey for years before this, using stuffing made from boiling water (I'm lazy so I always use the mix) and hadn't managed to poison myself, but the logic behind the advice does seem sound - I just don't follow it myself :-)