Set frozen pie shell out to thaw. Set oven to 350 degrees. Spray cooking oil in a large iron skillet. On top of stove, add raw chopped onion and cut up chicken to the skillet. Sprinkle the Cavender's greek seasoning, salt and pepper evenly over the mixture and cook for about 15 minutes over medium heat, stirring occasionally until chicken is cooked through on all sides and onion is transparent.
Drain chicken mixture and transfer to a large mixing bowl. Add a can of mushroom soup, sour cream, and frozen vegetables. Stir until thoroughly mixed.
Wash and dry the same iron skillet and spray lightly with cooking spray. Place one of the pie crusts in the bottom of the skillet. Pour the chicken/vegetable mixture on top of the pie crust and spread it out evenly. Top with a second pie crust.
Slide the skillet into your preheated oven and bake for 35 minutes, or until the top pie crust is golden brown. Enjoy!