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, black pepper, red pepper flakes, 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 they are cooked through and golden brown.
While the meatballs are baking, prepare the quinoa or rice according to package instructions.
In a serving bowl, layer the cooked quinoa or rice, followed by the cherry tomatoes, cucumber, red onion, and feta cheese.
Once the meatballs are done, place them on top of the salad mixture and drizzle with tzatziki sauce.
Serve with lemon wedges on the side for an extra burst of flavor.