Preheat your oven's broiler. Prepare a baking sheet by lining it with foil and spraying it generously with cooking spray.
In a large mixing bowl, combine the ground beef, eggs, breadcrumbs, diced onion, salt, pepper, and garlic powder. Mix thoroughly until the ingredients are well incorporated.
Form the mixture into 1-inch meatballs and arrange them on the prepared baking sheet.
Broil the meatballs for 8-10 minutes, or until they achieve a golden brown exterior.
While the meatballs cook, prepare the sauce. Melt the grape jelly in a microwave-safe bowl by heating it in 30-second intervals, or use a saucepan over medium heat.
Once the jelly is melted, whisk in the chili sauce until fully combined.
Spray the inside of a slow cooker with cooking spray. Place the cooked meatballs into the slow cooker and pour the sauce evenly over the top. Stir gently to coat the meatballs with the sauce.
Cover and cook on the low setting for 3 hours.
Before serving, garnish with chopped parsley for a fresh and colorful touch.