Preheat the oven to 375°F (190°C).
In a mixing bowl, combine ground beef, breadcrumbs, Parmesan cheese, parsley, egg, minced garlic, salt, black pepper, and oregano. Mix until all ingredients are well combined.
Form the mixture into 8 equal-sized meatballs, about 1.5 inches in diameter.
Place the meatballs on a baking sheet lined with aluminum foil. Bake in the preheated oven for 20 minutes, or until cooked through.
While the meatballs are baking, heat a skillet over medium heat and pour in the marinara sauce.
Once the meatballs are done, add them to the skillet and simmer for 5 minutes to warm the sauce and allow flavors to meld.
Slice the slider buns in half and place a meatball on each bottom half. Top with a generous spoonful of marinara sauce and sprinkle with mozzarella cheese.
Place the sliders back on the baking sheet and put them in the oven for an additional 5 minutes, or until the cheese is melted and bubbly.
Remove from the oven and place the top half of the buns on each slider. Serve warm.