3 1/2pound roast ought to do it....3 bones.

Hmmm. I was recently at a dinner with a 3 bone rib roast for 4 of us (3 of us women) and there was not a lot left over.

I made prime rib a while back for five adults who I'd qualify as one light eater, three medium, then me. I bought a four rib roast (from the loin end - the smaller end but bigger eye and less fat, ribs 9-12) and it looked too big so I cut off and froze the smallest rib. We had plenty but no leftovers. That said, my father is a well-done heathen so he gladly ate the ends which are not what I'd typically serve someone initially unless they specifically wanted it.

So my vote is 3 rib if you're not concerned about cutting it close, perhaps less for you if it doesn't end up looking like enough, or four rib if you don't want to worry about it, and are fine with the expense and leftovers which you will likely have.

and what about serving. What is the proper way to slice it?

I cut it off the bone before cooking (not hard if you have a sharp, long enough knife but you could ask your butcher to do it) then tie it back onto the bone for roasting. Then at serving time you simply cut the string and you have a boneless roast which you can easily slice as thin or thick as you'd like, I go for about a half inch. I don't like dealing with the bone while slicing and serving.

And that roasted bone makes the best beef stock!

Interesting about cutting off the bone. Does
that affect roasting time? BTW, do you all sear your roast before putting
it in the oven? My mom did it that way. My store puts a pop up timer in, but the
searing melts it. I have to use a thermometer, which no one ever trusts.

Dialogue:

Husband: the dial is not moving: those
things never work. It’ll be overdone.

Me: I bought a new one, so you wouldn’t
worry about it.

Him: the dial is not moving: those things
never work.

Me: it worked fine using a thermometer last
year.

Him: I don’t remember. I thought it was
terrible.

Me: that was the duck, the year before. The
beef was fine last year. Rare, just the way everyone likes it.

Him: the dial is not moving: those things
never work.

Most butchers will do that without asking....and the bone is tied back on so if you roast it with the meat, makes no difference.

If you have leftovers, you can make stock with the bones and then make vegetable soup with the leftover meat and stock. I like to add barley, onion, celery, carrots, tomatoes, green beans, and turnip.

Leftover prim rib is too good for soup!...Warm it a little, or not and make a sandwich, or slice on top of a salad.

There are charts for figuring amounts and this is from the chart I keep in my Price Book for figuring price per serving - not just price per pound:

Boneless - 4 (3-oz.) servings per pound

Some bone - 3 (3-oz.) servings per pound

Much bone - 2 (3-oz.) servings per pound

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Rib meat - 3/4 - 1 pound per person

Bone-in - 1/3 - 1/2 pound per person

Boneless - 1/4 - 1/5 pound per person

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Bone-in beef = 1/5th waste

A general rule of thumb is one rib per two people. However that does not yield much in the way of leftovers, or second helpings. For five, you should be ok with a three bone, but a four rib will make plenty of sandwiches for a few days after, and don't forget roast beef hash! mmmmm :)

As far as cutting the bones off and tying them back on, never heard of this, and curious to know the reasoning? I've never found cutting the bones off after cooking to be difficult, on the contrary, carving a rib roast is like slicing a loaf of bread, easy peasy...

Here's Martha with a quick show how...

4 ribs to be on the safe side, small end roast. Never buy the large end if you can avoid it: more fatty, the center strip meat narrows out.

We love beef, so I make a 3-rib roast for 2 people (no sides except a green salad). Roasted/sliced one night; sandwiches the next. Sliced rib-eye meat topped with Gruyere and black pepper, on good English muffins, is sooooo good.

I rub the rib bones with a wet chili rub and broil quickly for a BBQ lunch: one for me, two for DH. DH can clean a bone off so it almost sparkles! A dog would starve to death chewing on his leftover bones.

Not fond of beef broth except when making borscht, so we toss the bones in the compost cart that the city picks up weekly. I prefer poultry/pork broth, which is more versatile.

My method is quite different than the one posted above, this is how I've done it for over 40 years and never failed me yet...

Pepper only, no seasoned salt, or herbs, unlike a bird, IMO prime rib needs no other flavors, (except horseradish when served;)

I do not use a rack as the bones act as a rack.

I start off at 450* for the first 20 minutes, then lower to 250* until an instant read measures 120* in the center, no longer, it continues to cook.

Remove the roast, crank the oven back up to 450* to make Yorkshire pudding while the roast rests for at least 20 min.

I always serve with creamed spinach, this year I'm adding Pioneer Woman's whisky glazed carrots, along with some some Parsnips or Turnips.

I'll be doing this Christmas night for my wife and myself at our Baja hideaway...

¡Feliz Navidad!

If you roast it all the way in a hot oven it may smoke.....but the low and slow, tent it and then back into the blazing hot oven won't fill your house with smoke....might create a little but not a lot. We did that last Christmas, it was perfect....and I sure don't remember any smoke.
We had simple baked potatoes ( in the other oven) and roasted asparagus....and Yorkshire puddings!
I would also like oven roasted potatoes and something stupid simple like peas with a butter tarragon sauce. ( cook peas in a bare spoonful of water....knead butter with cornstarch, add to the peas with a bit of dried tarragon...and a splash of broth or white wine if you need a big more liquid.

Come on! It's once a year treat.

$4.99 a lb on sale here in NYC

Bought a ton. Cut off one bone yesterday for testing, Sous vided at 129F tasted great. Perfection guaranteed.

Going to buy another ton later. :-)

dcarch

Thanks for all the
suggestions. I bought the roast today. The largest they even had was 3 ½
pounds. I took a good look at the sides, looks like a good proportion of meat
vs. fat. I should have bought on Sunday when there were more size choices, but
I was afraid it might be too long to hold it til Friday. I bought it at a
different store today, so no pop-up timer. Dcarch, I paid $ 9/lb, almost twice that! I pay 4.99/lb for pot roast (not willingly: grumble, grumble...)

It looks like none of you
sear the meat first?

Interesting idea, going slow
at first and finishing on high. 175 F is the lowest my oven goes.

If you take it out when the thermometer
registers 120 F for medium rare, how much standing time can you allow? An
advantage of finishing it on the higher temperature would be that I would have
enough time for the Yorkshire pudding to cook. That needs a hot oven too. I
could start baking that, then pop the roast in for the last 10 minutes.

I bought asparagus to go with
it. I have not decided how to prepare that yet. They are very thin.

I have done it with all the searing methods, torch, grill, broil, pan sear --- they all work well.

One thing I do is to put the roast in the freezer for about 15 to 20 minutes after SV and that gives me more time to sear without overcooking.

The timing in the freezer depends on if your freezer is in the defrost cycle or not.

dcarch

After seasoning the roast, I rub a layer of flour on the fat cap. It cuts down on smoking from fat spritzing and makes a nice golden crust.