Preheat the oven to 375°F (190°C) and lightly grease a 9x13-inch baking dish.
Spread the uncooked rice evenly across the bottom of the baking dish.
In a separate bowl, whisk together the chicken broth, lemon juice, minced garlic, salt, and pepper.
Place the cubed chicken and diced red onion over the rice layer.
Pour the broth mixture over the chicken and rice, ensuring all rice is submerged.
Cover the dish tightly with aluminum foil and bake for 35 to 40 minutes, or until the rice is tender and the chicken reaches an internal temperature of 165°F.
Remove from the oven and let rest covered for 5 minutes.
In a small bowl, combine the Greek yogurt, squeezed cucumber, and dried dill.
Gently fold the yogurt mixture and crumbled feta cheese into the warm casserole until creamy and well-combined.