Combine oil, lime juice, vinegar, onion, garlic, chili powder, salt and cumin in large glass dish.
Pound steak to 1/4 inch thickness.
Place steak in marinade; turn to coat.
Cover and refrigerate overnight or several hours, turning several times.
Drain steak; discard marinade.
Grill steak, on covered grill, over medium-hot with Mesquite Charcoal Briquets 4 to 8 minutes on each side or until done.
Cut bread into 1-inch slices and toast on grill.
Arrange steak, sliced into 3/4-inch diagonal strips, on toasted bread.
Tbp with hot salsa and guacamole.