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Amanda is a co-founder of Food52.
At 350 degrees F, 20 min per pound if defrosted, and 10 to 15 min if the bird is fresh. During the last hour of cooking, though, I would keep checking the turkey with a thermometer, rather than relying on time.
According to Butterball, 3.5-4 hours unstuffed, 4.5-5 hours stuffed. I agree with Amanda, temperature is the best guide. For food safety, the stuffing has to get to at least 165F, and the middle of the thigh has to be 180F. (Alton Brown insists stuffing a bird with room-temperature stuffing means the meat will be overcooked, especially on the breast, before the stuffing is hot enough. He suggests microwaving the stuffing briefly to get it hot before packing it into the bird.)
Oh, and per Butterball, those times are in a 325F oven.
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