Step 1

If the roast has a fat cap more than 1/4 inch thick, trim it with a sharp knife or ask your butcher to do it for you. Tie the roast between the bones with butcher's twine. This discourages the eye of the meat from separating from the cap.

Step 2

In a small bowl, whisk together the Dijon mustard, Worcestershire sauce, garlic, thyme, and rosemary. If the dried rosemary leaves are long, finely chop them before adding.

Step 3

Slather the outside of the roast with the mustard paste and season generously with Traeger Prime Rib Rub on all sides. Refrigerate uncovered for 8 hours.

Step 4

When ready to cook, set the Traeger temperature to 250℉ and preheat with the lid closed for 15 minutes.

Step 5

Insert the probe into the center of the prime rib, avoiding the bones and any large pockets of fat. Place the prime rib directly on the grill grates, fat-side up. Roast until the internal temperature reaches 125℉-130℉ for rare or for 135 °F for medium-rare, 3 1/2-4 hours.

Step 6

Transfer the roast to a cutting board with a deep well. Loosely tent with foil and let rest for 30 minutes.

Step 7

Remove the twine. Use a sharp knife to remove the rack of bone following the curvature of the meat, then carve the meat against the grain into 1/2-inch-thick slices. Serve with horseradish, if desired. Enjoy!