Bring water, oregano and salt to a boil in large saucepan.
Add grits gradually, stirring constantly. Reduce heat to MEDIUM-LOW; cover. Cook 8-10 minutes or until thickened, stirring occasionally. Stir in 1½ cups cheese and sour cream; cook 1-2 minutes or until cheese is melted, stirring constantly.
Serve grits topped with sausage and remaining cheese. Garnish with parsley, if desired.