If you haven't already, cook and cool your chicken. Poach, bake, or use a rotisserie chicken. Shred or dice into bite-sized pieces.
In a large bowl, whisk together mayonnaise, Greek yogurt, lemon juice, salt, pepper, and garlic powder until smooth.
Core and dice the apple into small cubes (leave the peel on for color and texture). Roughly chop the toasted pecans.
Add the chicken, apple, pecans, red onion, and parsley to the bowl with the dressing. Stir gently until everything is evenly coated.
Taste and adjust seasoning if needed. Cover and refrigerate for at least 30 minutes before serving to let the flavors meld.