Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large bowl, combine ground chicken, breadcrumbs, Parmesan cheese, parsley, garlic, oregano, salt, pepper, and egg. Mix until well combined.
Form the mixture into meatballs, about 1 inch in diameter, and place them on the prepared baking sheet.
Drizzle olive oil over the meatballs and bake for 20-25 minutes, or until cooked through and golden brown.
While the meatballs are baking, prepare the quinoa according to package instructions.
In a large bowl, combine cooked quinoa, cherry tomatoes, cucumber, and red onion. Toss gently to mix.
To serve, place a scoop of the quinoa salad in a bowl, top with meatballs, sprinkle with feta cheese, and drizzle with tzatziki sauce.