Combine olive oil, lime and lemon juice, lime zest, cilantro and garlic in a shallow pan.
Cut the fish into 4 even portions and add them to the marinade. Using a sharp knife, make 2 slices into each portion to allow the marinade to seep into the fish.
Place in the refrigerator and marinate for at least one hour. Turn every 20 minutes.
Heat the grill to high. Place the fish on the grill and cook for 5 minutes. Spoon the marinade evenly over the fish. Close the grill cover and cook on high for 1-2 minutes.
Open the grill. Lower the heat to medium and cook until the fish is cooked through, usually about 5 more minutes.
Nutritional information per serving: 243 calories, 17 g fat, 3 g saturated fat, 91 mg cholesterol, 80 mg sodium, 4 g carbohydrates 0 g fiber, 20 g protein.