In a large saucepan combine onion, carrots, garlic, and water. Bring to boiling; reduce heat. Cover and simmer about 10 minutes or until vegetables are tender, stirring occasionally. Do not drain.
Stir in milk, oat bran, parsley, salt, nutmeg, and pepper. Bring to boiling over medium-high heat, stirring constantly. Cook and stir for 2 minutes. Remove from heat. Stir in cheese until melted. Cool slightly.
In a large mixer bowl beat egg whites until stiff peaks form (tips stand straight). Fold in vegetable mixture.
Pour into an ungreased 1-1/2-quart souffle dish. Bake in a 325 degree F oven about 50 minutes or until top is brown and a knife inserted near the center comes out clean. Serve immediately. Makes 4 servings.