PREHEAT oven to 350ºF. Cook pasta in large saucepan as directed on package; drain. Meanwhile, combine tomatoes, tomato paste, oregano and garlic; reserve 1/2 cup of the tomato mixture for later use.
DRAIN pasta; place in large bowl. Add remaining tomato mixture, the ricotta cheese, spinach and 1/2 cup of the shredded cheese; mix lightly. Spoon into 8-inch square baking dish sprayed with cooking spray. Top with reserved 1/2 cup tomato mixture and remaining 1/2 cup shredded cheese.
BAKE 25 to 30 min. or until heated through.