Prepare the Meatballs: In a large mixing bowl, combine the ground turkey, breadcrumbs, Parmesan cheese, parsley, minced garlic, dried oregano, onion powder, salt, black pepper, and the beaten egg. Mix until just combined, being careful not to overwork the meat mixture.

Shape the Meatballs: Using your hands or a small scoop, form the mixture into meatballs, about 1½ inches in diameter. You should get about 16-18 meatballs.

Cook the Meatballs: Heat a drizzle of olive oil in a large skillet over medium heat. Add the meatballs in a single layer, being careful not to overcrowd the pan. Cook the meatballs for about 4-5 minutes on each side, or until they are browned and cooked through (internal temperature of 165°F/74°C). Remove from the skillet and set aside.

Make the Tzatziki Sauce: In a small bowl, combine the Greek yogurt, grated cucumber (with excess moisture squeezed out), minced garlic, dill, lemon juice, and a pinch of salt and pepper. Mix until smooth. Taste and adjust seasoning if needed.

Serve: Serve the turkey meatballs warm with the tzatziki sauce on the side. Pair with pita bread, a Greek salad, or roasted vegetables for a complete meal.