Preheat the oven to 350F. Lightly grease a 9"x13" baking dish and set aside.
Cut the zucchini into small bite-sized pieces. Cut up the 3 cooked chicken breasts into small cubes, or shred enough chicken for 3 cups.
5 cups Zucchini, 3 cups Cooked Chicken
Combine in a large mixing bowl, (enough to fit all of the ingredients), the Greek yogurt, cream of celery, shredded cheese, oregano, salt, garlic powder. Whisk until smooth.
1 medium Yellow Onion, 1 can Cream of Celery, ¾ cup Greek Yogurt, 1 cup Marble Cheese, 1 teaspoon Salt, 1 teaspoon Garlic Powder, 1 teaspoon Oregano
Add to the large bowl, the cubed or shredded chicken, and the zucchini pieces. Stir until everything is well coated. Fold in 2 cups of the cubed bread.
3 cups Bread
Transfer the contents of the mixing bowl to the lightly greased baking dish. Spread out the mixture to level and sprinkle the remainder of the bread cubes.
Bake the Chicken and Zucchini Bake in the preheated oven for 40 minutes, or until golden brown. Remove from the oven and rest for 5 minutes before serving.