Preparation - In a large mixing bowl stir the sliced onions, minced garlic, salt, and pepper and beer together. Add the bay leaves. Place the venison roast in this marinade. Marinate in the refrigerator for 12 to 24 hours, turning the roast occasionally. Drain the roast and discard the marinade, reserving the onions. Place the roast and onions in a slow cooker. Add 1 cup barbecue sauce. Cover and cook on low for about 8 to 10 hours. Heat the remaining 1 cup barbecue sauce to serve with the roast. Makes 6 to 8 servings.