Heat 1/2 cup water and soy sauce in a large pot, then add the onion, bell pepper, and garlic and cook over medium heat until the onion is translucent and most of the water evaporates.
Cut the squash in half and remove its seeds, then peel and cut it into 1/2-inch cubes. Add squash cubes to the onion mixture, along with the chopped tomatoes, remaining 1 cup water, oregano, chili powder, cumin, and pepper. Cover and simmer until the squash is just tender when pierced with a fork, or about 20 minutes, then add the kidney beans with their liquid and the corn. Cook 5 minutes longer.
Nutrition information per 1-1/2 - cup serving: 185 calories, 6 g protein, 38 g carbohydrate, 0.8 g fat, 4% of calories from fat, 0 mg cholesterol, 314 mg sodium