Melt margarine in a large Dutch oven coated with cooking spray over medium-high heat. Add onion; sauté 5 minutes. Stir in consommé, broth, water, and pepper; bring to a boil. Reduce heat, and simmer, uncovered, 35 minutes. Add wine, and simmer, uncovered, 5 minutes.
Place bread on a baking sheet; sprinkle with cheese. Broil 2 to 3 minutes or until cheese is golden. Ladle soup evenly into bowls; top each serving with a bread slice.