Preheat the oven to 375°F (190°C).
Heat olive oil in a large oven-safe skillet or casserole dish over medium heat.
Add the diced onion and cook for 3-4 minutes until softened.
Add the minced garlic and cook for 1 minute until fragrant.
Add the chicken pieces to the skillet and cook for 5-6 minutes until lightly browned on all sides but not fully cooked through.
Stir in the uncooked rice, frozen peas, frozen diced carrots, and frozen corn kernels.
Pour in the chicken broth and water, then add dried thyme, dried parsley, salt, and black pepper. Stir to combine.
Bring the mixture to a gentle boil on the stovetop.
Cover the skillet or casserole dish tightly with a lid or aluminum foil and transfer to the preheated oven.
Bake for 35 minutes until the rice is tender and the chicken is cooked through.
Remove from the oven and carefully remove the lid or foil.
Sprinkle the shredded cheddar cheese evenly over the top of the casserole.
Return to the oven uncovered and bake for an additional 5 minutes until the cheese is melted and bubbly.
Let the casserole rest for 5 minutes before serving.