Preheat oven to 350°F (175°C) and lightly grease a 9x13-inch baking dish.
Slice the slider buns in half horizontally, keeping the bottoms together. Place the bottom halves in the prepared baking dish.
Spoon marinara sauce evenly over the bun bottoms, then place one meatball on each roll.
Top with more marinara, mozzarella, and Parmesan cheese. Place the top halves of the buns over the meatballs.
Brush melted butter over the tops of the buns, then sprinkle with garlic powder and Italian seasoning.
Cover with foil and bake for 15 minutes. Remove foil and bake another 5 minutes until golden and melty.
Garnish with parsley, pull apart, and serve warm.
Prep Time: 10 minutes | Cook Time: 20 minutes | Total Time: 30 minutes
Kcal: Approx. 310 per slider | Servings: 12