Turkey often gets overcooked because the breast often gets done before the legs. But if the turkey is frozen, the breast actually takes longer to cook, which means the whole turkey has a better chance of being cooked through to a safe 165 degrees F at the same time.
The important thing to remember when cooking a frozen turkey is that you'll need about 50% more time. And you never want to cook a partially thawed turkey. Make sure it is either completely frozen or completely thawed.
Click here to see a video on how to cook a frozen turkey.
Turkey image by Stephanie Gallagher 2012, licensed to About.com Inc.