In a Dutch oven over medium heat, saute the onions and garlic in the oil for 1 minute. Add the broth, water, beans, potatoes and oregano. Cover and bring to a boil. Reduce the heat and simmer for 15 minutes, or until the potatoes are tender.
2
Puree about three-fourts of the soup in a blender or food processor. Pour the puree back into the pot and heat through. Add salt and pepper to taste. Stir in the tomatoes and basil.