We had a large number of people over for the holiday (Saturnalia) yesterday. We roasted three, 20+ lbs. turkeys, but this year we used a method called "spatchcocking". We did this for a single, smaller bird at Thanksgiving and were thrilled with the results.
Each turkey cooked in 60 - 75 minutes and turned out perfect. Basically, you cut out the backbone and spread the turkey out flat (sort of) and roast it at 450 degrees. This method produced some of the best tasting turkey I have ever had and it sure was energy efficient.
Here is a video from the New York Times which explains the method for anyone who is interested.