Heat broiler on HIGH. Heat oil in 10-inch nonstick skillet on medium heat. Add peppers and onions. Cook, stirring occasionally, until vegetables are soft. Stir in roast beef.
Meanwhile, stir together steak sauce and teriyaki sauce in small bowl. Cut French bread into 2 (6-inch) loaves. Separate and place, cut side up, on large cookie sheet. Spread sauce evenly over each piece of bread.
Mound beef mixture over each piece of bread. Top with Marble Jack cheese cubes.
Broil with tops of sandwiches 4-6 inches from heat for 2-3 minutes or until cheese is melted.