Preheat the oven to 400°F (200°C).
In a large bowl, combine the ground turkey, breadcrumbs, onion, garlic, egg, parsley, oregano, salt, and black pepper.
Mix gently until just combined, then form into 1-inch meatballs.
Place the meatballs on a baking sheet lined with parchment paper.
Bake for 20-25 minutes, until cooked through and golden.
While the meatballs are baking, prepare the tzatziki by mixing yogurt, grated cucumber, lemon juice, minced garlic, and salt in a bowl.
Chill the tzatziki in the refrigerator until ready to serve.
Once the meatballs are done, serve hot with tzatziki on the side.