In a 13" x 9" baking pan, mix flour, salt, pepper and Italian seasoning.
Toss the chicken in the seasoned flour to coat. Set aside.
In a Dutch oven, pour enough oil to coat the bottom. Set it over medium-high heat. Heat till oil is shimmering hot. Without crowding the pot, add chicken pieces to the pot and cook until browned nicely on all sides.
Place the browned chicken on a plate and set aside. Do not discard the remaining flour mixture.
Add more oil to the Dutch oven, if needed. Add onion and mushrooms (and peppers if using) and saute until the vegetables soften, about 5 minutes.
Add garlic and cook 30 more seconds
Add the remaining flour and stir until it dissolves into the oil. Cook, stirring constantly until the flour is browned, about 2 minutes.
Add wine and bring it to a boil.
Add chicken broth and tomatoes and stir. Return to a simmer.
Return the chicken to the pot along with any juices on the plate. Cover and place in the oven.
Cook until the chicken is falling off the bone, about 6 hours.