Preheat oven to 350 degrees F. Spray a 9x13-inch baking pan with nonstick cooking spray; set aside.
Cook rice according to package directions and spread in an even layer in the bottom of prepared pan; set aside.
Melt butter in a saucepan over medium-high heat and whisk in flour. Cook for 1 minute, stirring continually. Gradually whisk in chicken broth and cook until mixture begins to thicken, about 3 minutes.
Remove from heat and mix in chicken, Greek yogurt, sour cream, Worcestershire sauce, garlic powder, salt and pepper until well combined. Spread mixture over rice in an even layer.
In a small bowl, combine all topping ingredients and sprinkle on top. Bake for 30 minutes, or until lightly golden brown on top.