In a large bowl, combine the cooked chicken, red grapes, red onion, and celery.
In a small bowl, whisk together the mayonnaise, lemon juice, salt, garlic powder, onion powder, and black pepper. Taste and adjust seasoning if needed.
Stir the dressing into the main ingredients until well combined.
Serve immediately or store in an airtight container for 3 to 5 days. Discard if left out for more than 2 hours.
Notes
For best flavor, refrigerate the salad for at least 30 minutes before serving. Always keep refrigerated and consume within the recommended time frame.