How does one prepare a frozen smoked turkey leg?  How long should it bake in the oven after you defrost it?

If it is completely thawed out I would guess 20 to 30 min at 350˚.

its probably already cooked so bake till its at what ever temp you want to eat it at.

To properly cook anything you need to cook it to temperature. That means using a digital temperature probe.

A smoked turkey leg is already cooked.   Putting it back in the oven may dry it out.   Wrap in foil, use an oven bag or steam it in a steamer pan or just put it in the microwave. 

Smoked turkey leg is fully cooked. 

Thaw it and bring it to temperature that you want it.  It could also be used cold, a turkey salad sandwich or just sliced on a sandwich would taste great. 

It's already fully cooked ... all you need to do is heat it up .