In a large, heavy skillet over medium high heat, heat oil. Slit sausage casing; remove meat and crumble into skillet. Cook, stirring often, for about 2 minutes or until beginning to brown.

Add onion and continue to cook for about 3 minutes or until meat is cooked through and onion is softened. Drain off any excess fat.

Stir in tomatoes, oregano and hot pepper sauce. Bring to a boil, reduce heat and simmer for 5 minutes or until slightly thickened. Add cream cheese a little at a time, stirring constantly, until melted. Gradually add mozzarella, stirring until melted. Transfer to a serving dish and serve warm. (Can be made ahead and reheated in the microwave).