Any kind! I've tried pork, beef, chicken, and turkey meatballs - and I think veggie meatballs would also work really well as a vegetarian option! This recipe is very forgiving - it can work with meatballs that are pre-cooked, and I've also enjoyed this recipe with the pre-made, UNCOOKED meatballs that you can often buy in the meat department. For a specific brand, I really enjoyed these with the u003ca href=u0022https://www.instacart.com/products/19243559-mild-italian-style-meatballs-16-ozu0022u003eALDI pre-made uncooked Italian style meatballsu003c/au003e (I know, wrong flavor profile, but it worked just fine and the meatballs were amazing). I just brushed them with the harissa sauce before baking.