Put the frozen meatballs in the slow cooker. Add the grape jelly and chili sauce.
Stir until the meatballs are coated in the grape and chili sauce mixture.
Place the lid on the slow cooker.
Cook on HIGH for 2.5-3 hours or LOW for 4-5 hours. Stirring occasionally so the meatballs won't burn on the edges.
Stove-Top Instructions:
Add everything to a large pot. Turn to medium low heat, heat for about 15 minutes or until the meatballs are warmed and the sauce starts to thicken.
Video
Notes
How to keep grape jelly meatballs warm at a party:Turn the slow cooker to warm. They can be kept warm at a party for 3+ hours. Stir often, and add a splash of water if the sauce thickens too much.