Place the flour, salt and pepper in a large resealable plastic bag; add chicken and shake to coat. In a large skillet, brown chicken in oil over medium heat for 3-1/2 to 4 minutes on each side. Remove and keep warm.
In the same skillet, saute the onion, mushrooms and green pepper until crisp-tender. Stir in the ketchup, water and sherry or broth. Add chicken; cook, uncovered, over medium heat for 14-16 minutes or until juices run clear and sauce is thickened. Serve with rice. Yield: 2 servings.