HEAT oven to 350ºF.
COOK pasta in large saucepan as directed on package, omitting salt. Drain pasta, reserving 1/2 cup cooking water. Return pasta and reserved water to pan.
ADD artichokes, spinach, peppers, 1-1/2 cups mozzarella and Parmesan; mix lightly. Pour into 2-qt. casserole sprayed with cooking spray; top with remaining mozzarella.
BAKE 25 min. or until heated through.