Heat oven to 375°F. In 10-inch skillet, heat oil over medium-high heat. Add onion and celery. Cook 3 to 5 minutes, stirring occasionally, until crisp-tender. Stir in carrots, green beans, chicken, soup, gravy and sage. Cook until bubbly. Stir in 3/4 cup of the cheese. Spoon into ungreased deep 2-quart casserole.