- In a large bowl. combine the juice of the 2 limes, garlic, cilantro, 2 tablespoons of the oil, vinegar, salt, cumin, oregano, pepper and chili powder. Whisk together until well-blended.  
- Add beef, cover and marinate in the refrigerator for about 30 minutes to 1 hour. Turn occasionally. 
- In a bowl, combine bell peppers, onions, 1 tablespoon of the oil and juice of the remaining 1 lime. Season with salt and pepper to taste. Gently toss to fully coat and set aside. 
- Drain meat from marinade and pat dry. Discard marinade.  
- In a wide pan over medium-high heat, add bell peppers and onions and cook, stirring regularly, for about 1 to 2 minutes or until tender yet crisp. Remove from pan and keep warm. 
- In the same pan, heat remaining 2 tablespoons oil until hot. Add beef and cook for about 6 to 8 minutes or until cooked through.  
- Return bell peppers and onions and toss until heated through. 
- In another pan, heat tortillas for about 30 seconds on each side or until warm and pliable. 
- To assemble fajitas, divide meat and vegetable mixture onto warmed tortillas. Serve with guacamole, pico de gallo and lime wedges.