In a large skillet, saute celery, onion and garlic in margarine until tender. Add broth, potatoes, carrots and pepper; bring to a boil. Reduce heat; cover and simmer for 15-20 minutes or until potatoes are tender.
Uncover and simmer for 5 minutes or until broth has thickened slightly, stirring occasionally. Sprinkle with parsley; serve with a slotted spoon.