To prepare a vidalia sweet onion chicken breast casserole casseroles recipe, you will first need to prepare the ingredients for the casserole. You will need the following ingredients: 1 1/2 cups Vidalia Sweet Onion Casserole Mix 2 tablespoons chopped scallions 1/2 cup chopped red bell pepper 1 tablespoon chopped celery 1 teaspoon each ground black pepper and cayenne pepper 1/4 teaspoon ground thyme 1/2 teaspoon kosher salt 1 cup shredded cheddar cheese 2 teaspoons each chopped parsley and dill 1 pound rotisserie chicken Breasts Bake in the oven at 350 degrees F for 30 minutes or until chicken is cooked through.