In large saucepan or Dutch oven, melt margarine and add onion, celery and scallions. Cook over medium-high heat, stirring occasionally, 3 minutes. Stir in mushrooms; cook 1 minute longer.
Add remaining ingredients and 2 cups water. Bring to a boil; reduce heat; cover partially and simmer 20 minutes. Ladle evenly into 8 soup bowls.
