Place the beef chuck roast into the bottom of a 6-quart slow cooker.
In a medium bowl, whisk together the cranberry sauce, BBQ sauce, orange juice, brown sugar, mustard, and spices.
Pour the sauce mixture over the beef, ensuring it is well coated.
Cover and cook on the LOW setting for 8 to 10 hours (or HIGH for 5 hours) until the beef is fork-tender and shreds easily.
Remove the beef from the slow cooker and place it on a large platter.
Shred the beef using two forks, removing any excess fat.
Skim any fat from the remaining liquid in the slow cooker.
Return the shredded beef to the pot and toss it with the sauce to coat thoroughly.
Serve warm, garnished with fresh cranberries if desired.