Marinate steak in combined TACO BELL Fajita Seasoning Mix, water and 1 Tbsp. oil for 10 minutes.
Grill steak on hot greased grill 8 to 10 minutes on each side or until cooked through. Cut into thin strips.
Cook and stir pepper and onion in 1 Tbsp. oil in large nonstick skillet on medium high heat 5 minutes or until tender. Stir in steak strips. Heat tortillas as directed on package. Spoon steak mixture onto each tortilla. Top as desired.