Spray the insert of the slow cooker with nonstick cooking spray to prevent sticking.

Dump the frozen meatballs directly into the slow cooker insert.

In a mixing bowl, whisk together the beef broth, brown gravy mix, onion soup mix, ketchup, and Worcestershire sauce until smooth and well combined.

Pour the sauce mixture over the meatballs and gently stir to coat.

Cover with the lid and cook on LOW for 5–6 hours.

In a small bowl, mix 2 tablespoons of cornstarch with 2 tablespoons of cold water to create a slurry.

Stir it into the slow cooker and cook for an additional 10 minutes, or until the gravy thickens.

Serve hot over mashed potatoes or egg noodles, and garnish with chopped parsley if desired.