Preheat the oven to broil. Line a baking sheet with foil then spray it with cooking spray.
In a medium bowl, combine beef, breadcrumbs, salt, pepper, garlic powder, oregano, egg, and water. Mix well and add more water if needed for a smooth texture.
Scoop approximately 2 tablespoons of the meat then roll it into a ball. Press a cube of cheese into the center of the meatball. Surround the cheese with meat and re-roll the ball. Place the meatball onto the prepared baking sheet. Repeat until all meatballs are rolled and stuffed with cheese.
Lightly spray the meatballs with cooking spray. Place in the oven on broil for 10 minutes or until the meatballs are just done (overcooking will cause the cheese to spill out).
Pour warm marinara sauce over the meatballs then sprinkle with fresh parsley. Serve.