Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper and lightly coat it with cooking spray.
In a large bowl, combine the ground chicken, red onion, feta cheese, dill, mint, lemon zest, lemon juice, breadcrumbs, egg, olive oil, garlic powder, salt, and pepper.
Using a cookie scoop or spoon, portion approximately 2 tablespoons of mixture and roll into meatballs. Place them evenly on the prepared baking sheet.
Bake for 20 minutes or until the Greek Chicken Meatball Bowls meatballs are golden brown and reach an internal temperature of 165°F (75°C).
While the meatballs cook, prepare the rice or orzo according to package instructions.
In a large bowl, whisk together the dressing ingredients. Add the cucumber, tomatoes, bell pepper, olives, red onion, herbs, and feta cheese. Toss well to combine.
Prepare the yogurt dill sauce by mixing together the Greek yogurt, lemon juice, dill, garlic powder, salt, and olive oil until smooth.
Assemble the bowls by dividing the rice among serving bowls. Top with meatballs, cucumber salad, and yogurt dill sauce.
Garnish with additional feta cheese, parsley, or fresh herbs if desired.