HEAT oven to 400°F.
ADD oregano to coating mix in shaker bag; use to coat chicken as directed on package. Place in 13x9-inch pan.
BAKE 20 min. or until chicken is done (165°F). Meanwhile, cook pasta in large saucepan as directed on package, adding spinach to the boiling water the last minute.
TOP chicken with 1/2 cup sauce and cheeses; bake 3 min. or until mozzarella is melted. Drain pasta mixture; return to pan. Add remaining sauce; cook until heated through, stirring frequently. Serve topped with chicken.