In a medium-sized bowl, whisk together lime juice, orange juice, olive oil, vinegar, salt, pepper, cumin, oregano and garlic. Pour into a 9×12-inch baking dish.
Add flank steak. Turn to coat both sides in marinade. Cover with plastic wrap and place in fridge to marinate for up to 4 hours. Remove meat and discard marinade.
Preheat gas or charcoal grill to 400°F.
Place steaks on oiled grates and grill steaks 8-10 minutes on one side or until moisture starts to pool on the top and beef releases easily from grates with tongs. Flip once, grilling on the other side for 8-10 minutes or until internal temperature reaches 145°F with meat thermometer inserted into the thickest part of the steak.
Transfer steaks to a platter and let rest for 5-10 minutes before slicing against the grain.
Serve with rice, beans, guacamole and tortillas.
Nutrition information per serving: Calories 280; Total fat 15g (Sat. fat 5g; Trans fat 0g); Cholest. 100mg; Sodium 280mg; Total Carb. 2g; Fiber 0g; Total Sugars 1g; Protein 32g; Vit D (0% DV); Calcium (4% DV); Iron (15% DV); Potas. (15%DV)