Marinate skirt steak in 1/2 cup of dressing for two hours; remove from marinade and discard dressing. Grill until internal temperature of steak reaches 145°F; slice thin. Baste red onion rounds with oil and grill with steak.
Mix baby greens, grilled red onions and sliced steak with a 1/2 cup of dressing until well coated.
Remove to serving plate; top with tortilla strips.