In a mixing bowl, whisk together olive oil, lime juice, orange juice, garlic, cumin, chili powder, salt, pepper, and oregano.

Place the flank steak in a resealable plastic bag and pour the marinade over it. Seal the bag and refrigerate for at least 1 hour, preferably overnight.

Preheat the grill to medium-high heat.

Remove the steak from the marinade and discard the marinade. Grill the steak for about 5 minutes on each side for medium-rare, or until desired doneness.

Let the steak rest for 5 minutes before slicing it against the grain.

Serve the sliced carne asada with chopped cilantro, diced onion, lime wedges, and salsa on the side.