2 prime ribs

[Fishingfarmer]

I need to make prime rib for tomorrow night. I bought a 20 lb full ribeye. I just checked and it wont fit on any of my plans. I will either have to run to Walmart and find something for it, or cut it in half and make both at once. Has anyone done this? Googled it and people have done it. Nobody mentions how long I need to cook it. Is it like making a 10 lb roast, or like 20 lbs of meat? I'm sure the oven will run longer. It is 20 lbs of meat. The heat is able to enter through the cut side so can heat quicker also.

Any tips would help. I need it done around 730 for the fire dept. It's my turn to cook. I would like it hot and fresh, not undercooked or cold. If anyone is worried, its way over budget (all volunteer dept so budget is low), but I'm donating it so it doesn't matter.

[SteveDyer]

It's like two seperate roasts so you would base your time on 10lbs. I'd cook it till it was 123° IT then let it rest wrapped a min. of 30 min. It will take about 15 min/pound at 325° and 35min/lb in a smoker at 225°

[Curt Wilke]

This is from my notes for a 10 lbs 4-bone Prime rib. Let the Prime Rib sit out at room temp for 4 hours before cooking. Smoker was at 260 degrees and the internal temp of Prime Rib was 56 degrees. Pulled the Prime Rib from the smoker at 128 internal degrees, 4 hrs 15 mins. My smoker is a reverse flow Lang 84 Deluxe. There is a lot of air flow with a reverse flow smoker so it should be similar in cooking time to an oven set on "convection roast". You can let a Prime Rib sit for 30 to 90 mins after it is pulled from the heat. I usually tent it with a pc of Al foil if I know it will sit longer than 30 mins.