Heat the oil in a large, heavy flameproof casserole dish or deep frying pan. Add the onions, garlic and rosemary and cook gently, stirring frequently, for about 15 minutes until soft and golden.
Add the chorizo and capsicums and cook over a medium heat, stirring frequently, for a couple of minutes or until the sausage turns slightly golden.
Add the sun-dried tomatoes, the canned tomatoes with their juice, and the wine. Season with freshly ground black pepper (salt should not be needed), then stir well and bring to a simmer.
Add the chicken and stir to coat with the sauce. Bring to the boil, then reduce the heat so the sauce simmers. Cover and cook for 25–30 minutes until the chicken is tender and the sauce is thick.
Just before serving, stir in the pitted olives and cook for just long enough to heat them through.