1Preheat your oven to 375°F (190°C).
Cook the rice according to the package instructions.
While the rice is cooking, dice the chicken breast into bite-sized pieces.
In a large skillet, sauté the diced chicken breast over medium heat until fully cooked, about 5-7 minutes.
Dice the medium onion and add it to the skillet with the chicken. Cook until the onion is translucent, about 3-4 minutes.
Add the mixed vegetables to the skillet and cook for another 2-3 minutes.
In a large mixing bowl, combine the cooked rice, chicken, onion, and mixed vegetables.
Stir in 1 cup of shredded cheese until well mixed.
Transfer the mixture to a baking dish and spread it out evenly.
Sprinkle an additional layer of shredded cheese on top if desired.
Bake in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let it cool for a few minutes before serving.