In a bowl, combine olive oil, orange juice, lemons, limes, salt, pepper, and garlic cloves, saving juiced fruit. Whisk together. Place chicken legs, juiced pieces of fruit, and quartered onions in large plastic bags or bowl. Pour marinade over the top, tossing to combine. Cover with plastic wrap (if using bowl) and marinate for at least two hours--several hours is better. Toss a few times during the marinating process.
Preheat broiler to high. Arrange oven rack toward bottom of oven.
Lay chicken legs on a broiler pan, or other baking dish with a drip tray. Broil for 25 minutes, turning once and marinating other side halfway through. Remove pan from oven when done.
Wrap tortillas in foil and warm in separate oven while chicken is broiling, or after chicken is removed from oven (reduce oven temp to 300.)
Serve chicken legs with warm tortillas, pico de gallo, beans, guacamole, sour cream, and/or salsa verde.