Heat oil in a large frying pan over medium high heat. Sauté chicken breasts for 4 to 5 minutes each side, or until white. Add pepper, garlic, onion and stock. Cover and simmer over medium heat until stock cooks off, about 7 to 10 minutes.
Stir in pasta sauce, then cover and simmer another 10 minutes, or until chicken is cooked through and no longer pink inside. Sprinkle cheese on top, cover and cook for another 2 to 3 minutes, or until cheese is melted. Serve hot.