Cooked a 6 lb. prime rib yesterday.
According to the "book" I needed to cook at 350 for 20 minutes per lb. = 180 minutes or 3 hours, to get medium rare.

Checked temp. at 2.5 hours, and it was 170 degrees already, and well done instead of medium rare.
Should have been pulled at 130 degrees. (CRAP!)
Forgot to factor in pulling it out of the fridge two hours before cooking, to let it get to room temp. BIG mistake!!!

It was still eatable, but not great like it would have been

Valuable lesson learned here!!

Virgil B.