Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish.
Dice the chicken breast into one-inch bite-sized pieces and place them in a large mixing bowl.
Add the broccoli florets, sliced carrots, and chopped red bell pepper to the bowl with the chicken.
In a separate small bowl, whisk together the Greek yogurt, chicken broth, Dijon mustard, garlic powder, onion powder, dried thyme, sea salt, and black pepper until smooth.
Pour the yogurt herb sauce over the chicken and vegetables, tossing thoroughly to ensure every piece is well coated.
Transfer the mixture into the prepared baking dish, spreading it out into an even layer.
Sprinkle the shredded sharp cheddar cheese evenly over the top of the casserole.
Bake for 25-30 minutes, or until the chicken is cooked through and the cheese is golden and bubbling.
Remove from the oven and let the casserole rest for 5 minutes before serving to allow the sauce to thicken.