Preheat oven to 450°. In a separate mixing bowl, toss chicken with black pepper and oregano, and olive oil, mixing until well coated and set aside.
Add Knorr® Pasta Sides™ - Chicken Flavor, sliced tomatoes, and seasoned chicken in 13 x 9-in. baking dish. Stir in water and milk. Mix well, and ensure all pasta is submerged in liquid. Top with ½ cup of crumbled feta cheese and bake 20 minutes.
Remove baking dish from oven and stir well. Return the dish to the oven and bake for an additional 10 minutes, or until chicken is thoroughly cooked. Remove from oven and stir in chopped spinach. Top with remaining crumbled feta. Let cool 5 minutes before serving.