Place chicken, flour, chili powder, 1/2 teaspoon salt, and 1/2 teaspoon ground black pepper in a plastic bag. Seal and shake to coat.
In a 4- to 6-quart Dutch oven cook chicken mixture, onion, and garlic in hot oil over medium heat until browned. Add undrained tomatoes, broth, potato, corn, and quinoa. Bring to boiling; reduce heat. Simmer, covered, 15 to 20 minutes or until potatoes and quinoa are tender.
Stir in spinach and lemon juice and cook just until spinach is wilted. Garnish each serving with shredded lemon peel. Makes 6 servings.