Prime Rib Roast: The Slow-Roast Method

Perfect slow-roasted prime rib
DebbiSmirnoff / Getty Images
  • 21 hrs
  • Prep: 16 hrs,
  • Cook: 5 hrs
  • Yield: 4 to 8 servings
Ratings (160)

Prime rib is a large piece of meat, but just because it's big doesn't mean you can treat it roughly. It's big, yes, but it's from the beef rib primal, so it's also tender. As with anything tender, it's best to be gentle with it. 

To a tender rib roast, a hot oven acts like a hand squeezing water out of a sponge. Only instead of springing back like a sponge, meat stays squeezed. The result: a dry, shrunken roast.

That's why the best way to cook prime rib is to roast it gently. A low temperature doesn't squeeze, so there's little to no shrinkage, and the juices stay in the meat. The result: juicy, prime rib perfection.

The only catch is that the oven doesn't get hot enough to brown the exterior. We have to do that ourselves, directly in the roasting pan, across two burners on the stovetop. So make sure you have a heavy-bottomed roasting pan that's suitable for the stovetop.

This technique will work equally well for either a bone-in or boneless rib of beef of between 5 and 10 pounds. For a bone-in prime rib, figure two servings per rib, while a boneless roast will yield two servings per pound.

A couple of tips:

  • The night before you're going to roast, unwrap the meat and let it sit in the refrigerator, uncovered, on sheet pan with a rack. This will allow some of the surface moisture to evaporate, making it easier to get a beautiful brown crust when you sear it.
  • Three hours before you're going to roast it, take the meat out and set it on a sheet pan (to catch any juices) at room temperature. This step is important. If the meat is ice cold, the technique won't work as well. (And you don't have to worry about the meat going bad. Any surface bacteria are going to get seared immediately.)

What You'll Need

  • 1 boneless or bone-in beef rib roast, trimmed and tied
  • Kosher salt and freshly ground black pepper, to taste

How to Make It

  1. Pre-heat your oven to 200F. Set your roasting pan across two burners on your stovetop. Add a couple of tablespoons of high-heat refined canola oil and get it smoking hot. Then add the roast and carefully sear it on all sides. Use tongs for turning it rather than anything that pierces it like a fork. Sear it for a total of 7–8 minutes, until it's nice and brown all over.
  2. Season the roast generously with Kosher salt and freshly ground black pepper. For a boneless prime rib, put a roasting rack in the pan, and then set the roast on it fat-side-up. With a bone-in prime rib you can skip the roasting rack and set the roast bone-side-down in the roasting pan.
  1. Insert a digital probe thermometer into the deepest part of the meat, being careful not to hit bone. Set the temperature alert to beep when the meat hits 128F (see note below).
  2. Roast until the temperature reaches 128F, which will be another two-and-a-half to five hours, depending on the size of your roast.
  3. Remove from the oven and transfer to a cutting board and cover it with foil. Leave the thermometer in! Once you take it out, the temperature should nudge up to 130F, which is perfect medium-rare, and within 20 minutes or so it will drop back down to 120F, which is when it's fully rested and ready to slice and serve.

Note: Another advantage of slow roasting is that there's not much carryover cooking, so you don't need to rest the roast for very long. 

For medium-rare prime rib, we want to take the roast out of the oven at 128F, and it will continue cooking until it reaches 130F. If you prefer a medium prime rib, take it out at 135F with a target temperature of around 140F. Either way, you'll still want to rest the meat until it comes back down to 120F before carving it.

Here's a simple au jus recipe you can make while the meat is resting. Or try this creamy horseradish sauce.