Please help with cooking time of boneless prime rib?!

Doverengineer

I picked up an amazing 15lb piece of prime rib yesterday to bring to our family Christmas. Upon getting home and checking the length of the prime to my large egg it was apparent that I was going to have to cut it in half in order to get it to fit. So, I did that and seasoned it.
Now am no curious if cook time is for the full 15lb or if it's closer to 7lb. 

I want to cook this as late as possible to ensure that its still hot when my family (who is always running behind!) is finally ready to eat.

Going to clean out the egg...any help would be much appreciated!

YukonRon

Let it sit in ambient temperature, before cooking at 225F pit, 250F Dome, for about an hour. I used a place setter, legs up, meaning raised indirect. Since you have cut in half to cook, allow 30-45 minutes / pound of the smaller size, they should cook the same, pull at 120-130F IT, tent loosely with either foil or paper and let stand until you serve.It should keep it in the Medium Rare range.
I did one, using the above method on a low and slow, came out fabulous.
Wishing you good luck, and a Merry Christmas.

Darby_Crenshaw

It wouldn't take longer as one piece. It's a long chunk of meat, not a round ball of meat. 

Once your length is more than the width, the cook time is about the same no matter how big

Doverengineer

Thanks guys! It got done a little faster then planned but turned out great. Two family members were hesitant as they said they have never liked this cut of meat. They booth took leftovers home!