Baked Spaghetti & Meatballs

~20 fully cooked, frozen Italian Meatballs (I usually buy the 32 oz bag which comes with around 65-70 and just count out how many I need and save the rest for another recipe)

jar of pasta sauce of your choice

yellow onion, diced

garlic, minced

Italian seasoning

olive oil

spaghetti noodles

shredded mozzarella

grated parmesan