Season the chicken thighs with kosher salt and ground black pepper, then place them in a mixing bowl and pour 1/2 cup ranch dressing over the thighs; toss to coat and let sit for 10 minutes.
Heat 2 tablespoons olive oil in a large sauté pan over medium-high heat. Add the marinated chicken thighs and brown about 3 minutes per side, until lightly golden; transfer the chicken to a plate and set aside.
If needed, add a little more oil to the pan, then add 1 cup diced onion and 1 diced bell pepper; sauté 2–3 minutes until softened.
Stir in 1 1/2 teaspoons minced garlic and cook about 30 seconds until fragrant, then splash in a bit of the chicken broth to deglaze the pan.
Add 1 cup dry white rice to the pan and toast, stirring, for about 1 minute.
Stir in 1 cup frozen peas and carrots, 1 tablespoon ranch seasoning, and 2 cups low-sodium chicken broth; mix to combine.
Return the browned chicken thighs to the pan, nestling them into the rice mixture. Cover, reduce heat to medium, and cook for about 20 minutes, stirring sparingly, until the liquid is absorbed and the rice and chicken are cooked through.
Remove from heat, fluff the rice with a fork, adjust seasoning with salt and pepper if desired, and serve garnished with fresh parsley.
