1. Place the steak in a shallow glass baking dish.

2. In a small bowl, combine salsa, Worcestershire sauce, lime juice, oil, seasoning mix, and garlic; mix well.

3. Pour the marinade over the steak, cover it and refrigerate, turning occasionally for 4 hours or overnight.

4. Once the steak has marinated, prepare the grill for medium heat.

5. Remove steak from marinade, reserve marinade.

6. Grill steak, onions, and bell peppers, turning occasionally for 10 minutes, or until steak is medium-rare and vegetables are tender and lightly charred.

7. In a small saucepan, set the reserved marinade over medium-high heat and bring to a boil, stirring frequently for 2 minutes.

8. Thinly slice the steak diagonally across the grain.

9. Cut bell peppers into strips.

10. Place steak, bell peppers, and onions in warm tortillas; drizzle with salsa mixture.

11. Serve with beans, guacamole, and cilantro, if desired.