Preheat the broiler. Line a sheet pan with foil and coat the foil with cooking spray.
Place the beef, breadcrumbs, salt, pepper, garlic powder, oregano, egg and water in a bowl; mix until thoroughly combined. You may need to add more water, 1 tablespoon at a time, to get a smooth mixture.
Take approximately 2 tablespoons of the meat mixture and roll it into a ball. Press a cube of cheese into the ball of meat, making sure that the meat completely surrounds the cheese. Place the meatball on the sheet pan and repeat with remaining meat and cheese.
Spray the tops of the meatballs with cooking spray. Broil for 10 minutes or until meatballs are just done - do not overcook or the cheese filling may start to spill out.
Place the meatballs on a plate and pour the marinara sauce over the top, Sprinkle with parsley and serve immediately.
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