Make the dressing by combining the remaining ingredients in a separate bowl. Then toss dressing with chicken mixture until it is coated evenly. Adjust seasoning as needed.

Preheat oven to 400°. Line a sheet pan with parchment paper. Coat chicken with olive oil, then season with salt and pepper. Lay chicken flat on the sheet pan and roast in oven for 10-15 minutes until a temperature of at least 165° is reached.

Let chicken cool, then shred with two forks or dice into chunks. Transfer to a large bowl. Add grapes and celery.