Preheat the oven to 350 degrees F. Spray a 2-quart casserole dish with nonstick cooking spray.
Heat the oil in a large skillet set over medium-high heat. Add the onions. Cook and stir 5 minutes. Reduce the heat to medium-low; cover. Continue cooking until the onions are golden, 13 to 15 minutes, stirring occasionally.
Heat the butter in a large saucepan set over medium-high heat. Cook and stir the celery and turkey bacon until the celery is crisp-tender, 6 to 8 minutes. Stir in the chicken broth and stuffing mix; mix lightly. Stir in the cooked onions and corn.
Spoon the mixture into the casserole dish; cover. Bake until heated through, 35 to 40 minutes.