will the bottom be soggy?
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HalfPint is a trusted home cook.
My sister does this with her turkey. If I remember correctly, you will get drippings, but not the crispy skin. I don't remember her complaining that the bottom gets soggy, but I do know that the meat is extremely moist, even the breast portion.
Forget the roasting bag. Drying overnight will help ensure crispy skin as will using a shallow pan with turkey on a rack. You'll have drippings, but watch that they do not burn- add water to pan if needed. If using drippings for gravy, taste before adding any additional salt.
pierino is a trusted source on General Cooking and Tough Love.
Skip the bag as you are risking disaster. My brother did this one year and what came out of the oven resembled turkey stew. But then my brother is a terrible cook. I was summoned to the kitchen but it was already beyond repair.
AntoniaJames is a trusted source on Bread/Baking.
Also, if you brine it, you'll get salty drippings, so be careful! Buy and roast an extra wing, and the neck, in a separate pan for the best gravy drippings in these circumstances. (The advantage to that: you can do it, and make gravy, the day before Thanksgiving.) ;o)
I've had, and enjoyed, turkey cooked in a bag. Moist and tasty , but definitely nothing crispy about the skin. So what I did when asked to "take over the kitchen " a couple if years ago was took it out of the bag, retain the juices for the gravy, dried off the skin with paper towel and put the bird back in the oven to crisp the skin. Turned out great. Brine? not when your bagging it. There's enough moisture in the bag.
Put some root veggies, or a slatted tray, under the bird (in the bag) to keep the bottom out of the liquid.