Remove the casings from the Italian sausages and cut or tear into 1 inch pieces.
Heat the olive oil in a large skillet over medium heat. Brown the sausage pieces until browned on all sides, stirring to ensure proper browning. This may take 5 or 6 minutes. Remove the sausage pieces and set aside.
Add the onions to the pan, stirring to coat with the oil. Season with a few pinches of salt and a little pepper. Cook until the onions have started caramelizing and softening, about 15 minutes. Add the sliced peppers, garlic and Italian seasoning and cook until the peppers soften, about 5 minutes or so. Return the peppers to the pan, add the chicken broth, tomato sauce or wine and cook until the peppers have heated through and the liquid has reduced, about 5 minutes or more. Adjust seasoning with some more salt and pepper if needed.
Serve over gluten-free pasta , rice, or polenta and top with chopped parsley and Parmesan cheese, if desired. These also make delicious, hearty sandwiches stuffed into toasted gluten free sandwich rolls.