Preheat your oven to 400°F (200°C).
In a large bowl, combine ground meat, breadcrumbs, Parmesan, parsley, egg, garlic, salt, and pepper.
Mix until well combined and form into 12 equal meatballs.
Place meatballs on a baking sheet lined with parchment paper.
Bake in the preheated oven for 15-20 minutes or until cooked through.
While the meatballs bake, prepare your slider buns and toppings.
Slice the slider buns in half.
Once meatballs are done, remove from the oven and let cool for a few minutes.
Assemble sliders by placing a meatball on each bun and topping with cheese, lettuce, tomatoes, and onions.
Serve warm and enjoy your delicious meatball sliders!