Directions

1. Trim fat from steak and place steak in a resealable plastic bag. For marinade, stir together oil, lime juice, fajita seasoning and oregano. Reserve and refrigerate 2 tablespoons of the marinade. Pour remainder over meat, seal bag and refrigerate 4 to 24 hours, turning occasionally.
2. Preheat grill to medium (300°F to 350°F). Place onion slices on an 18-inch sheet of heavy-duty foil. Drizzle with reserved marinade. Bring up 2 opposite sides of foil and double-fold to seal. Fold the ends to completely enclose onions, leaving room for expansion. Wrap tortillas separately in foil.
3. Remove steak from marinade; discard marinade. Grill steak 7 to 9 minutes per side for medium-rare (140°F). Place onion packet on grill during last 10 minutes of grilling time. Add wrapped tortillas during last 5 minutes.
4. Thinly slice meat, place in warm tortillas with onions and mango, and serve immediately.