Dry stuffed pepper

I would definitely include tomato in the stuffed pepper filling. Saute a dollop of Tomato Paste until brick red at the end of the cooking time for the rest of your sauteed vegetables, and add the quinoa, then stir in more tomato sauce or broth until you get a filling that will stick together a bit. Add a little water to loosen if needed.

whenever i use a vegetable as a casing for a meat stuffing (i love big zukes stuffed with gr. lamb/hamburger, onions, chopped tomatoes) and usually add an egg as a binder but also add a good amount of liquid to more resemble meatloaf. you can add v-8, tomato juice, milk if no lacto problem, broth, etc., along with some bread crumbs. you could do this with quinoa. sautéing your veggies before adding them removes a lot of the natural liquid that they contain.

You might try tossing the peppers unto a gas burner (assuming you have one) and blackening the outer skin. When the skin is blistered nicely toss them in a paper bag, close it tightly and let it sit for 20 minutes. Then rub off the charred bits of skin. You won't get all of it but don't worry about that. Meanwhile you can cook your quinoa and saute your onions. You might also add a chunk of a good melting cheese like fresh mozzarella or even a triple cream like brie. Roast in the oven at no more than 350F. You can use this method with your basic super market green pepper but it's even better with stronger flavored ones like passilla or Anaheims. Hatch pepper season should be only a few weeks away.