1. Season the beef with the salt and black pepper.
2. Heat 1 tablespoon oil in a 4-quart heavy saucepan over medium-high heat. Add the beef in batches and cook until well browned, stirring occasionally.
3. Add the water to the saucepan and heat to a boil. Reduce the heat to medium-low. Cover and cook for 1 hour or until the beef is fork-tender.
4. Remove the beef to a cutting board. Using 2 forks, shred the beef. Reserve cooking liquid from saucepan.
5. Cook the sausage, onion and garlic in the saucepan over medium heat until the sausage is well browned, stirring often to separate meat. Pour off any fat.
6. Stir in the soup, 1 1/2 cups reserved cooking liquid, beef and oregano and heat to a boil. Reduce the heat to medium-low and cook, uncovered, for 15 minutes.
7. Divide the beef mixture among the tortillas. Fold the tortillas around the filling.
Serving Suggestion: Top the beef mixture with your favorite taco toppings before folding the tortillas. The beef mixture is also delicious used as a filling for enchiladas, quesadillas or burritos.