In a large saucepan, combine the first 10 ingredients. Bring to a boil. Reduce heat; cover and simmer for 15 minutes.
Uncover and return to a boil. Process oats in a blender or food processor until ground; gradually stir into soup. Stir in milk. Simmer for 10 minutes, stirring constantly. Remove from the heat. Cover and let stand for 3-5 minutes before serving.