Preheat the oven to 375°F and lightly grease a 9x13-inch baking dish.
Toss the chicken pieces with the olive oil, ½ teaspoon of the granulated garlic, ½ teaspoon of the onion powder, ½ teaspoon of the thyme, ¼ teaspoon of the salt, and ⅛ teaspoon of the pepper until evenly coated.
Spread in a single layer in the prepared baking dish. Bake uncovered for 10 minutes until the chicken is lightly golden at the edges and just beginning to cook through.
To the par-baked chicken, add the sour cream or Greek yogurt, mixed vegetables, ½ teaspoon of granulated garlic, ½ teaspoon of onion powder, ½ teaspoon of thyme, ¼ teaspoon of salt, ⅛ teaspoon of pepper, and 1 cup of the cheddar.
Stir gently until everything is well combined, smoothing the chicken vegetable mix into an even layer. Sprinkle the remaining ½ cup of cheddar evenly over the top.
Cover tightly with foil and bake for 10 minutes.
Remove the foil and bake uncovered for 5-10 minutes, or until the cheese has melted and the sauce is bubbling around the sides.
Let rest for 5 minutes before serving, as the sauce will continue to thicken as it cools.