Cooking the meatballs on a rack over a baking sheet allows the fat to drip down away from the meatballs, cutting their fat content. That's especially important if you use beef, but even turkey has its fair share of fat.
You can vary the ingredients you add endlessly, and I no longer bother to measure much when I'm doing this, I just do it by feel.
TURKEY (Or Beef) MEATBALLS
1 package ground turkey (about 1.3 pounds on average) or 1 pound ground beef
2 oz breadcrumbs (plain or flavored) or 2 oz oatmeal
2 oz Parmesan cheese
1 egg (beaten)
chopped onion to taste (I use dehydrated onion for this)
Preheat the oven to 350 degrees. Line a baking sheet with foil and place a wire rack on the sheet.
Mix all the ingredients thoroughly.
Use a tablespoon or a cookie scoop (or your hands) to make small meatballs. This mix holds together well and is easy to work with.
Place the meatballs on the wire rack. Bake for 10 minutes, flip and bake for 10 minutes more.
Optional: I like to place the meatballs under the broiler for a few minutes more so that the tops brown and a bit more fat drips below.