Preheat oven to 375 F. Spray a 13×9-inch baking dish with nonstick cooking spray.

Cook the pasta according to package directions. Drain and set aside.

In a pan over medium heat, heat the olive oil. Add the spinach, garlic, ½ teaspoon ground black pepper and ½ teaspoon salt and sauté for a few minutes until wilted down and the spinach seems shrunken down in size. Allow to cool and set aside.

In a medium bowl, stir together 1 cup of the mozzarella, feta, and remaining ground black pepper and salt together, and the spinach mixture. Set aside.

In the baking dish, Pour ¾ cup of marinara sauce to cover the bottom.

Fill each shell with about 1 ½ tablespoons of the spinach cheese mixture, then arrange the shells on top of the sauce side by side until packed together.

Add remaining sauce in between or over shells, and sprinkle with remaining mozzarella cheese.

Bake for 25 minutes until cheese is bubbling. If they start to brown, cover with foil until finished. Enjoy!