Slow Cooker Cheesy Mushroom Meatballs

INGREDIENTS:
1 (64 oz.) package fully cooked (frozen) meatballs, thawed
2 (10.75 oz.) cans condensed cream of mushroom soup
1 (8 oz.) package button or baby portobello mushrooms, sliced
1 (16 oz.) package velveeta cheese or sharp cheddar cheese, cut into cubes
1 yellow onion, finely chopped
to taste salt and pepper
optional egg noodles, for serving
DIRECTIONS:
Place thawed meatballs in the slow cooker.
Top with sliced mushrooms, chopped onion, cream of mushroom soup, and cubed Velveeta or cheddar cheese.
Season with salt and pepper to taste.
Toss everything together until evenly coated.
Cover and cook on high for 3 hours or on low for 4-5 hours, stirring halfway through, until cheese is melted and sauce is smooth.
Serve hot, optionally over egg noodles or rice.