Depends on how you cook them. I would fry them up in a pan with a little oil to brown them on all sides (about 10 minutes). Then, it depends on whether or not you're going to put them in a marinara sauce, or serve them as appetizers.
If you put them in a sauce, you want to make the sauce first, and add the meatballs last, then cook them for another 10-15 minutes, until they are cooked through. You don't want them to be mushy anymore.
If you want to serve as an appetizer, just put them in the oven, after you saute them. I'd say around 350 degrees for about 10-15 minutes.
