Combine ground beef, breadcrumbs, Parmesan cheese, onion, egg, garlic powder, Worcestershire sauce, salt, and pepper in a large bowl. Mix until well combined.
Shape the mixture into meatballs about 1.5 inches in diameter, making around 12-15 meatballs.
Heat olive oil in a skillet over medium heat. Brown the meatballs on all sides for 5-7 minutes, then remove from skillet.
In a slow cooker, combine cream of mushroom soup, beef broth, soy sauce, thyme, onion powder, and black pepper. Stir until well blended.
Add the browned meatballs to the slow cooker, ensuring they are submerged in the gravy. Cook on low for 6-8 hours or high for 3-4 hours.