Pour 1/2 cup milk into small saucepan over medium heat. Combine remaining 1/4 cup milk and flour in a small bowl, stirring with a whisk until well blended. Gradually stir flour mixture and 1/4 teaspoon salt into warm milk, stirring constantly with a whisk. Bring mixture to a boil, stirring frequently; cook 1 minute, stirring constantly. Remove from heat. Add the provolone cheese to the milk mixture, one slice at a time, stirring until cheese melts after each addition. Set cheese sauce aside.
Heat 2 teaspoons of the oil in a large nonstick skillet. Add beef and sauté 2 minutes or until beef loses its pink color, stirring constantly. Remove beef from pan. Add remaining 2 teaspoons of oil to the skillet. Add onion and remaining 1/4 teaspoon salt and black pepper and sauté 3 minutes. Add the pepper and mushrooms and continue to cook, stirring, for 5 minutes. Add the garlic and cook for 1 minute more. Return the beef to pan and cook 1 minute or until thoroughly heated. Remove from heat.
Place the saucepan with the cheese sauce over medium heat for a minute, whisking constantly, to reheat.
Divide the beef mixture evenly among bottom halves of hoagie rolls. Drizzle sauce evenly over beef mixture; replace top halves. Serve immediately.
Nutrition information per serving: