Sprinkle chopped onions over the bottom of the cooker. Place roast on onions. Combine the brown sugar, seasoning blend, pepper, and garlic powder. Rub over the roast. Pour the beef broth into the bottom of the crockpot.
Cover slow cooker and cook on low for 7 to 9 hours.
Carefully drain off liquids and discard.
Add the chopped bell pepper and beans to the pot roast. Cover and cook on high for 1 hour longer. Serves 6-8