Bell peppers are often stuffed with rice, vegetables and possibly some meat. There's a good example of that here: Doh! Stuffed Bell Peppers.
You might also try doing bell peppers stuffed with quinoa.
Quinoa is a good substitute for rice in most recipes, and can be cooked the same way. (Many people pronounce quinoa "keen-wah".) Quinoa has some bitterness in it, and white quinoa is slightly sweeter/less bitter than red quinoa.
Why quinoa instead of rice?
Quinoa contains a balance of 8 essential amino acids; By itself Quinoa is a fairly complete nutritional protein and includes lysine, as well as 7 other amino acids.
Ingredients (for two or three servings):
2 or 3 large bell peppers (or 3 or 4 smaller ones)
½ cup, or so, of Quinoa, boiled in water, then drained (or you could use rice)
2 tbs. olive oil, to sautee
2 small tomatoes, or 7 oz (½ can) diced tomato
3 or 4 (or more, if you like) garlic cloves, minced or pressed
4 or 5 oz. cheese, feta, or other favorite cheese (I like to use cheddar!)
1 tsp basil, 1 tsp oregano (or other seasoning you fancy, maybe some thyme, or something hot, peppers in peppers?).
If you want, add a little meat to this recipe-- a handful of diced chicken or beef or hamburger, cooked in advance. You'll need to steam those peppers and sautee the onions, then mix it all up, except for the cheese, and fill, top with the cheese, and bake.
Along the way, pre-heat the oven to 325F (163C). Cook the quinoa as you would cook rice. Use a rice cooker, or a pot on the stove, and stir. Rinse the peppers, cut their tops off, and cut away the seeds and the white inside parts. Then, rinse the peppers again and steam them until they are slightly soft, 10 or 15 minutes (steamer basket insert, or you can crumple some aluminum foil in the bottom of a pan). Have the oven going now at 325F (163C). Sautee the onions in a little oil. Add the tomato, garlic, cooked quinoa, basil and oregano, optional meat, and mix thoroughly (if the pan is not large enough, transfer all that to a mixing bowl).
Spoon the mixture into the bell pepper shells, top with feta cheese. Bake in a casserole dish for 30 minutes. Taste it and see if it's right.