Heat your oven to 400 degrees F. Line two baking sheets with parchment paper. Set aside.
In a large mixing bowl, use your hands (or a wooden spoon) to mix together 2 pounds ground beef, 1 cup Italian seasoned breadcrumbs, 1 tablespoon dried oregano, 1/2 teaspoon dried basil, 1/2 teaspoon garlic powder, 1/2 teaspoon salt, 1/4 teaspoon black pepper, 1 1/2 teaspoons Worcestershire sauce, 2 large eggs, and 1/2 cup milk until evenly combined.
Use a 1-tablespoon cookie scoop (or measuring spoon) to portion the beef mixture into meatballs onto the prepared baking sheets. Then use your hands to roll each scoop into a ball. Arrange the meatballs so they have space between them.
Bake for 20 minutes, or until the meatballs are browned and reach 160°F in the center.
Remove from the oven and let rest on the baking sheets while you make the sauce.
Sauce
Place a medium saucepan over medium heat. Pour 12 ounces grape jelly and 12 ounces sweet chili sauce into the pan. Cook, whisking often, until the sauce is just starting to simmer.
Transfer the meatballs to the slow cooker and pour the sauce all over them. Gently stir until the meatballs are evenly coated.
Serve immediately with toothpicks, or cover the slow cooker and set it to WARM for party serving. If desired, sprinkle the meatballs with chopped parsley for garnish.
Notes
For frozen meatballs: For frozen meatballs: Use fully cooked frozen meatballs and add them directly to the slow cooker with the warmed sauce. Heat on LOW until warmed through.
Make ahead: Bake the meatballs, cool completely, and refrigerate for up to 1 day or freeze for later.
Serving: Once heated through, keep the slow cooker on WARM. Stir gently occasionally. If the sauce thickens too much, stir in a splash of water.