Beef Bulgogi

Name: Beef Bulgogi
Ingredients: 1 1/2 pounds rib-eye steak, trimmed of excess fat; 1/4 cup soy sauce; 1 tablespoon hot chili sesame oil; 2 tablespoons dark-brown sugar; 6 garlic cloves, minced; 1 tablespoon finely grated fresh peeled ginger; 2 medium red onions, halved and cut lengthwise into 1-inch wedges; 1 green bell pepper, seeds and ribs removed, sliced into 1/2-inch strips; 4 teaspoons vegetable oil; 1 small head Boston lettuce, separated into leaves