HEAT oven to 375ºF.
MIX meat, bread crumbs, tomatoes, Parmesan, garlic, 1/4 tsp. oregano and egg just until blended; shape into 12 (2-inch) meatballs.
PRESS mozzarella cube into center of each meatball, completely enclosing cheese. Place on rimmed baking sheet sprayed with cooking spray.
BAKE 20 min. or until done (165ºF). Meanwhile, cook pizza sauce, dressing and remaining oregano in large saucepan until heated through, stirring occasionally.
ADD meatballs to sauce; stir to evenly coat. Cut baguette into 6 pieces; fill with meatballs. Top with any remaining sauce.