COMBINE steak and 1/4 cup of the dressing in glass bowl; cover. Refrigerate 1 to 2 hours to marinate, stirring occasionally. Remove steak; discard marinade.
COOK steak in remaining 1/4 cup dressing in large frying pan on medium-high heat 5 to 6 min. or until no longer pink. Remove steak; keep warm.
ADD peppers and onion; cook until tender. Add steak; cook until heated through. Serve in warm tortillas topped with cheese, sour cream and salsa.