Heat olive oil in a large skillet (I always use my cast iron skillet for this) over medium-high heat.
Add bell peppers and onion; season with 1-1/2 tablespoons of the fajitas seasoning mix and cook for 5 to 6 minutes, or until tender, stirring frequently.
Transfer vegetable mixture to a plate and set aside.
Add the sliced steak to the skillet; season with 1-1/2 tablespoons of the fajitas seasoning mix and cook for 3 to 4 minutes, or to a desired doneness.
Stir in the previously prepared veggies; continue to cook for about 2 minutes, or until everything is heated through.
Spoon prepared veggies and steak on warm whole wheat tortillas.
Top with cheese, sour cream and guacamole. (Optional - Not included in the Nutrition Information)
Nutritional info is an estimate and provided as courtesy. Values may vary according to the ingredients and tools used. Please use your preferred nutritional calculator for more detailed info.