In a large bowl, whisk together olive oil, soy sauce, lime juice, and brown sugar. Add steak and toss until coated. Marinate for at least 30 minutes, up to 2 hours. Remove steak from marinade and pat dry with paper towels. Season lightly with salt (remember that there's soy sauce in the marinade) and pepper. To grill: Preheat grill to medium-high. Place steak on grill and cook to your liking, about 6 minutes per side for medium-rare. (Cooking time will vary due to thickness of your steak.) To broil: Preheat oven broiler to high. Place steak on a sheet pan and cook, turning once halfway through, until cooked to your liking, about 6 minutes per side for medium-rare. (Cooking time will vary due to thickness of your steak.) Let rest before slicing and serving.