Heat oil in heavy large Dutch oven over medium-high heat. Add onions and garlic; sauté until tender, about 10 minutes. Add squash; sauté Add bell peppers and stir to coat with onion mixture. Add broth. Cover and simmer until squash is just tender, about 10 minutes.
Mix kale and sage into stew. Cover and cook until kale wilts, stirring occasionally, about 8 minutes. Add beans and olives and stir until heated through. Season to taste with salt and pepper.
Transfer stew to large shallow bowl. Sprinkle generously with cheese.