Preheat a smoker to 250 degrees F. If you are using a charcoal smoker and wood chips this may take some time. If using a Traeger, or another electric smoker, this usually only takes 10-15 minutes.
Set the prime rib roast on a large rimmed baking sheet. If the top has a thick fat cap, or tougher silver skin you can trim it off, but it is not necessary. If you decide to trim the fat, leave at least ¼ inch around the roast.
In a small bowl mix the salt, pepper, thyme, rosemary, and garlic powder.
Drizzle the Worcestershire sauce over the top of the prime rib roast and rub it over the surface. (Or brush it on with a basting brush.) Then sprinkle the spice rub over the surface, making sure to coat the roast on all sides.
Once the smoker reaches 250 degrees F, set the roast on the grates. Insert a meat thermometer deep into the center of the roast. Close the lid and smoke until the internal temperature reaches 120 degrees F, usually 3-4 hours. Do not exceed 125-130 degrees.
Once the roast reaches 120 degrees F, take the proime rib off the smoker and place it on a clean rimmed baking sheet. Cover with foil. Allow the prime rib to rest for 20-30 minutes before slicing.
When ready to serve, slice thick or thin rounds, from top to bottom. A serrated knife, long chef’s knife, or an electric knife work well for this.
For the Au Jus: As the prime rib rests on the baking sheet, it will produce drippings. Collect the juices and measure out ½ cup, or as much as you can get. You can add more drippings to the au jus after you slice the meat if needed.
Place the drippings in a small sauce pot and set over medium heat. Add in 1 tablespoon flour for thin au jus, or up to 3 tablespoons flour for thicker au jus. Whisk well and cook for 1-2 minutes.
Then whisk in the beef broth and wine (if using.) Whisk to make sure there are no clumps. Then bring to a simmer. Once the au jus is hot, and as thick as you like it, turn off the heat.
Serve the sliced prime rib with au jus over the top, or on the side for dipping.
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Notes
PRO TIP: Check the temperature after 2 hours. Although prime rib usually takes 25-30 minutes per pound, there are several variables that can affect the cooking time, including how consistent your smoker heats, whether your prime rib roast is bone-in or boneless, and the actual dimensions of the roast itself. If the roast is done much early than expected, you can rewarm it on the grill for 10 minutes, before serving.Leftovers can be stored in an airtight container in the fridge for up to 5 days, or wrapped well and frozen for up to 4 months.