Prime Rib cooks I need advice

[SweetHeatBBQnSC]

My step-mother called me yesterday and wants to do prime rib for my father's get together Sunday. She is looking at between 15-20 people. Two main questions right now.

1. How big of a roast do we need? I am sure it will be the only meat there.
2. How long will the cook take? (on average)

Thanks for any help trying to figure out if I have time for the cook on Sunday, never did one before so I am totally clueless.

 

[thirdeye]

I dislike the term.... but there are two 'rules of thumb' when buying a prime rib roast. First is one pound per person, and this works better for a boneless roast. The second is each bone will feed two people, so a 4-bone roast should feed eight people.

Other thoughts are, how many guests prefer an end cut, or do all guests prefer a middle cut? Are some guests big eaters? Do you want leftovers for sandwiches etc.?

I'm a fan of cooking a prime rib low-n-slow, for less shrinkage and very even doneness from end-to-end and across each slice. Here is a database of cook times which have been averaged from a considerable number of cooks. Tip #1: Do not go on time only, let temperature be your guide. Tip #2: have a warmed cast iron skillet on stand-by so you can brown a slice if anyone thinks their cut looks too rare. 20 seconds on each side, and plate the 'darker' side up to sort of fool the brain into thinking it's more done. If you put a little AuJus on the plate it will hide any red color the juice.

Using the 220°-250°pit temps, and a smaller boneless roast, you can expect a 5° to 8° rise in the internal temperature stated below while the roast is resting on the cutting board.. A larger bone-in roast might rise 8° to 12°. All the temperatures reported below are when the roast is still in the cooker, so take into account the rise.
4 pound roast - 220°-228° pit temp - 2 hours to reach 125°
5-1/2 pound roast - 230° pit temp - 3 hours to reach 125°
5-3/4 pound roast - 245° average pit temp - 3 hours 45 minutes to reach 127°
6-3/4 pound bone-in roast - 250° pit temp - 4 hours to reach 125°
7 pound roast - 250° pit temp - 3 hours 40 minutes to reach 123°
7 pound roast - 220°-228° pit temp - 3 hours 30 minutes to reach 125°
7.9 pound roast - 230° pit temp (dome temp) - 4 hours 5 minutes to reach 125°
8 pound roast - 250° - 275° pit temp - 4 hours to reach 122°
10 pound roast - 220°-228° pit temp - 3 hours to reach 120°
11 pound roast (4 bones) - 215° average pit temp - 4 hours 54 minutes to reach 125°
14 pound roast - 220°-250° pit temp - 4 hours 30 minutes to reach 125°
15 pound roast - 220°-250° pit temp - 4 hrs 50 min to reach 127°
19.5 pound roast (prime grade) - 240° pit temp (dome temp) - 4 hours 25 minutes to reach 124°

 

[robertm]

Third eye is far to modest. He's created a really valuable blog with tons of data. Here's a link that helped my out when cooking prime rib:

http://playingwithfireandsmoke.blogspot.com/1996/03/beef-standing-rib-roast-prime-rib.html

 

[wbratt1]

Not much to add after thirdeye, but I do a few a year and like to go low and slow like he suggested. I keep it simple with beef and just season with my SPOG. I like to pull mine off a little early (120-ish) and then let it rest for 20 or so minutes and then put it in a 600F oven for ~ 5 minutes to crisp up the bark. It's worked out well for me. I do have some that prefer it at a higher temp than I do so I give them the outside slices and save the middle section for others. Good Luck!

 

[Porcine Perfection]

Great write up thirdeye. The only thing I would add is don't let it intimidate you with its size and cost. I put off cooking one years for this reason. My brother bought me one for Christmas a few years ago and I haven't looked back. It really is just a bunch of ribeyes and we have all cooked those. I do like to tie boneless ones for even cooking. Other than, just watch your temps. My last one I used Oakridge SPOGOS with just a sprinkle of Black Ops.

 

[mchar69]

Just to add the last one I did in the oven until 118 and then out on the charcoal grill to sear the outside. Best one ever.

 

[thirdeye]

Great write up thirdeye. The only thing I would add is don't let it intimidate you with its size and cost. I put off cooking one years for this reason. My brother bought me one for Christmas a few years ago and I haven't looked back. It really is just a bunch of ribeyes and we have all cooked those. I do like to tie boneless ones for even cooking. Other than, just watch your temps. My last one I used Oakridge SPOGOS with just a sprinkle of Black Ops.

Heheheee, you are right. "The hardest thing about cooking a prime rib is writing the check".

One year a guy emailed me during the holidays because he bought a USDA Prime, full 7-bone roast that weighed 18 pounds from a custom producer. The price tag was around $400. Worst, it was his first one, and he had a lot of guests to impress and a LOT of questions. He was understandably nervous. After about 20 back-and-forth emails (some on cooking day), my inbox went silent. No word the next day either. I'm thinking the worst happened, but then got an email telling me it came out better than he could ever expect.

 

[jzadski]

Looks like you got all you need in a couple of very good replies here. All I have to add is that, the way you have been turning out briskets the rib roast is easy. It's just reading that thermometer unlike a brisket where it's more feel and such

 

[smoke ninja]

some good prime rib info

https://www.bbq-brethren.com/forum/showthread.php?t=150482

time is trick because it's more about diameter than weight. I cook at low temperatures and usually alot for 3-3.5 hrs