2. Add the sliced onion and bell pepper. Cook until softened, about 5 minutes.
3. Add the thinly sliced chicken to the skillet. Season with salt and pepper. Cook until the chicken is no longer pink, about 10 minutes.
4. Reduce heat to low. Sprinkle the shredded mozzarella cheese over the chicken and vegetables. Cover and cook until the cheese is melted, about 2-3 minutes.
5. Toast the hoagie rolls if desired. Spoon the chicken mixture into the rolls.