Make the marinade: In a large bowl or ziploc bag, mix together all of the ingredients for the port wine marinade.
Trim the beef: Use a sharp knife to trim any excess silver skin from the roast. You can leave the fat cap on or take it off.
Marinate overnight: Add the beef to the bag with the marinade and seal the bag, pressing out all of the air. Let it marinate in the refrigerator overnight.
Salt the beef: After marinating, remove the roast from the bag and allow the excess liquid to drip off. Place the roast on a wire rack set on top of a sheet tray. Season all sides of the beef with salt. Then place the sheet tray with the beef in the refrigerator for 4-5 hours to salt brine.
Prepare for smoking: Preheat your smoker to 250°F (121°C) with your choice of wood or pellets. (For this recipe, I used Smokin’ Pecan pellets.)
Using cooking twine, tie up the ends of the beef to tuck the tail-end piece in a little and add more girth to the roast. This helps the beef cook evenly and lock in more flavor.
Finish seasoning: Lightly season with the all-purpose seasoning. Generously season with the black pepper.
Smoke the beef: Add an internal meat thermometer to the beef. Place the roast on the top rack of the smoker. Cook until the internal temperature reaches 130°F (mine took about 3 hours.) *Smoked eye of round is best served rare to medium rare.
Let the beef rest for at least 10 minutes before slicing against the grain into very thin slices. Serve warm with horseradish cream sauce or your favorite accompaniments. *See notes for horseradish cream sauce recipe/sandwiches.