Preheat oven to 375°F. Grease a 9x13 pan.
Cook pasta 2 minutes less than package directions. Drain.
Toss chicken with olive oil, garlic powder, salt, and pepper.
Sear chicken 2–3 minutes per side in a hot skillet until just cooked through. Slice into bite-size pieces.
Stir Alfredo sauce and milk together in a bowl to loosen it up.
Mix pasta, chicken, and sauce together. Pour into the prepared pan.
Top with mozzarella and Parmesan.
Bake 15–20 minutes until bubbly and cheese is melted.
Sprinkle parsley, rest 5 minutes, then serve.