Heat oil in a large saucepan over medium heat. Add onion and celery; sauté 4 minutes or until onion is tender. Add potato and next 5 ingredients. Bring to a boil. Cover, reduce heat, and simmer 30 minutes or until potato is tender. Uncover and cool 10 minutes.
Place half of potato mixture in a food processor or blender; process until smooth. Pour pureed mixture into a large bowl; repeat procedure with remaining potato mixture. Return pureed mixture to saucepan; cook until thoroughly heated.