Combine first 13 ingredients in a large bowl, mixing well. Place one-fourth of mixture in container of an electric blender; process until almost smooth. Repeat procedure with remaining mixture. Cover and chill at least 3 hours. Transfer mixture to a large glass pitcher or bowl. Pour or ladle into individual serving bowls.
On a tray, arrange bowls of chopped green onion, chopped cucumber, chopped green pepper, chopped celery, and croutons to be sprinkled over each serving.