In a separate sauce pan, add the onion, ground sirloin and sausage. Cook & crumble until no longer pink. Drain & discard excess fat.
Add in the cooked quinoa to the meat/tomato mixture, stir to combine and taste for seasoning, adding more salt and/or pepper if desired. Use a large spoon to divide the mixture evenly among the pepper halves. Top with shredded mozzarella.
Carefully pour 1/2 cup of water into the bottom of the baking dish. Cover with foil and bake for 30 minutes at 350 (try not to let the foil touch the tops of the peppers - it will steal your cheese!). Remove foil and bake an additional 10 minutes, until cheese is melted and peppers are crisp-tender.
Sirloin and Sausage Stuffed Peppers https://yummynoises.com/sirloin-and-sausage-stuffed-peppers/