Preheat oven to 375 degrees Fahrenheit.
In a 9x13 inch baking dish, combine the uncooked rice, chicken broth, dried oregano, and garlic powder.
Evenly distribute the raw chicken cubes, red onion, and kalamata olives into the rice mixture.
Season with salt and black pepper.
Cover the dish tightly with aluminum foil and bake for 35 minutes.
Remove the foil, stir in the tzatziki sauce and lemon juice.
Top with crumbled feta cheese and bake uncovered for an additional 10 minutes or until chicken is cooked through and rice is tender.
Allow to rest for 5 minutes before serving.