Heat olive oil in a large, heavy pot over medium heat. Add onions, garlic and bell peppers. Cook for 10 minutes, stirring occasionally, until the vegetables have wilted. Add spices and cook for 1 minute longer, stirring to coat vegetables well with spices. Add tomatoes with juice, meat, and squash. Bring all to a boil, reduce heat to medium low and simmer, uncovered, for 20 minutes or until squash is tender. Add salt and pepper if desired. Add beans and cook 10 minutes longer to heat through.