In a mixing bowl, combine ground beef, ground pork, breadcrumbs, egg, salt, pepper, garlic powder, onion powder, and minced onions.
Mix gently until combined, then form into 1.5-inch meatballs.
Lightly spray the slow cooker with non-stick spray and place a thin layer of sauce on the bottom.
Arrange meatballs in a single layer inside the slow cooker.
In a separate bowl, mix ranch seasoning, pepperoncini peppers, butter, Worcestershire sauce, and cream of mushroom soup.
Pour the sauce over the meatballs, covering them evenly.
Cover and cook on LOW for 4-6 hours, or until the meatballs reach an internal temperature of 160°F.
Let rest for 10-15 minutes before serving.