1Heat oven to 375º. Cut each bell pepper lengthwise in half; remove seeds and membranes. Heat 2 inches water to boiling in 2-quart saucepan. Add pepper halves. Cook uncovered 1 minute; drain.
2Melt margarine in same saucepan over medium-high heat. Cook celery and 3 tablespoons of the onions in margarine about 5 minutes, stirring occasionally, until crisp-tender.
3Stir in bulgur, 1 1/2 cups of the broth and the seasoning salt. Heat to boiling; reduce heat to low. Cover and simmer 6 to 7 minutes or until liquid is absorbed. Stir in 3/4 cup of the cheese.
4Fill bell pepper halves with bulgur mixture. Place peppers, filled sides up, in ungreased square pan, 8x8x2 inches. Pour remaining broth into pan. Cover and bake 20 minutes. Sprinkle with remaining 1/4 cup cheese and 1 tablespoon onion.