Preheat broiler to high. Slice bell peppers into bite-sized pieces, discarding stems and seeds.
Spread the cut bell peppers across a large sheet pan and cover with ½ of the pepper-jack cheese.
Place sheet pan under broiler and broil until cheese is melted, about 2 min.
Top with the black beans, corn, and remaining cheese, and return to broiler to melt the second layer of cheese. Cook until cheese is completely melted and edges of pepper are beginning to brown. About 3 min.
Remove from oven and sprinkle with the sliced green onions before serving alongside salsa for dipping. You may also serve with fat-free sour cream if desired.