Remove and discard seeds and membranes from 2 peppers. Chop peppers.
Broil remaining 6 peppers on an aluminum foil-lined baking sheet 5 inches from heat 2 to 3 minutes on each side or until peppers look blistered. Place peppers in a large zip-top plastic freezer bag; seal and let stand 10 minutes. Cut peppers lengthwise down 1 side, leaving other side intact; remove and discard seeds and membranes. Keep peppers warm.
Melt butter in a large skillet over medium heat. Add green onions, and sauté 1 minute. (Do not brown.) Stir in chopped peppers, tomatoes, and 1/2 tsp. salt; cook 4 to 5 minutes or until tender. Add corn, and cook, stirring occasionally, 6 minutes.
Remove from heat. Stir in cheese until melted. Spoon mixture evenly into cavity of each broiled pepper. Garnish, if desired, and serve immediately.