Preheat oven to 425 degrees.
Spray a large baking sheet with cooking spray. Pour the veggies onto the baking sheet. Spread out into an even layer. Nestle the chicken thighs into the vegetables so that chicken and vegetables are an even layer. Place the 4 garlic bulbs in each corner.
Bake for 45 minutes or until the chicken reaches at least165 degrees and the vegetables are fork tender.
Once the dinner is pulled out of the oven, remove the garlic bulbs. Let cool for a few minutes, then remove the roasted garlic bulbs and return to the sheet pan dinner. Serve.