Preheat your air fryer to 400°F (200°C).
Pat the chicken breast dry with a paper towel and cut it into 1-inch bite-sized cubes.
Trim the woody ends off the asparagus spears and cut them into 2-inch pieces.
In a medium mixing bowl, whisk together the olive oil, lemon juice, lemon zest, dried oregano, garlic powder, sea salt, and black pepper.
Add the chicken cubes and asparagus pieces to the bowl, tossing thoroughly until everything is evenly coated in the marinade.
Place the chicken and asparagus into the air fryer basket in a single layer, ensuring they are not overcrowded to allow for proper air circulation.
Air fry for 10 to 12 minutes, shaking the basket halfway through the cooking time, until the chicken reaches an internal temperature of 165°F and the asparagus is tender-crisp.
Place the warm cooked quinoa in a bowl, top with the air-fried chicken and asparagus, and garnish with the crumbled feta cheese before serving.