To prepare a southwest garden stew recipe, combine the following ingredients: 1 chopped onion, 2 chopped celery stalks, 1/2 cup chopped garlic, 1 tablespoon dried or fresh oregano, 1/4 teaspoon kosher salt, and 1 teaspoon ground black pepper. Cook over medium-low heat until the onions are translucent and the garlic is fragrant, 5 to 7 minutes. Add the remaining ingredients and cook, tossing, until all ingredients are heated through. Season with salt and pepper to taste. Serve with sour cream and guacamole.