Cut chickens into serving pieces and season to taste with salt and freshly ground black pepper. Sauté chicken pieces in olive oil until golden brown on all sides. Add finely chopped onion and dry white wine, and cook over a high heat until wine is reduced to half the original quantity. Add chopped tomatoes and garlic; cover pan and simmer until chicken is tender.
In the meantime, sauté sliced green peppers in a little olive oil until tender. Serve with chicken.