Heat condensed cream of celery soup, water or broth, and onion soup mix in large saucepan until bubbly. Stir in chicken, heat through. Stir in rice and remove from heat.
To assemble, halve peppers lengthwise; remove stems, seeds, and membranes. Place pepper halves, cut sides up, in a large shallow baking or roasting pan. Divide chicken mixture among the pepper halves. Sprinkle with lemon-pepper seasoning.
Bake peppers, loosely covered with foil, in a 350 degree F oven about 45 minutes or until heated through. Top with cheese and return to oven, uncovered, about 5 minutes more or until cheese is just melted.