Bring pasta water to boil and preheat oven to 400°F.
Meanwhile, prepare peppers by slicing in half and cleaning out ribs and seeds. Place on baking sheet and roast for about 10-15 minutes. I like mine still on the crisp side.
Cook orzo according to "al dente" package directions. Drain and return to pot along with the alfredo sauce, chicken and ½ cup of mozzarella cheese. Stir to combine and heat until warmed through.
Fill peppers with alfredo mixture, sprinkle each one with the remaining mozzarella cheese and return to oven. Bake for 5-10 minutes, or until melted and bubbly. Finish with freshly ground black pepper and serve.
Notes
Bell peppers vary in size. Four large ones should be enough for the filling, but you might have to eyeball it!