Heat the oil in a heavy-based frying pan which can be used under the grill/broiler.
Cook the chicken until golden. Remove and keep hot. Add the onion and peppers to the pan and saute gently until softened. Stir in the garlic. Return the chicken to the pan. Add the tomatoes, wine or chicken broth and oregano, and salt and pepper.
Bring to the boil. Cover the pan tightly, lower the heat and simmer for 30-35 minutes or until the chicken is tender.
When the chicken is thoroughly cooked, stir in the cannellini beans. Cover the pan again and raise the heat slightly. Leave to simmer for about 5 minutes more, stirring once or twice, until the beans are hot. Preheat Broiler.
Sprinkle the breadcrumbs evenly over the mixture in the pan and grill until the crumb topping is golden brown. Serve immediately.