Cut off the top of the peppers and make sure you get all the seeds out. Coat the insides of the peppers with olive oil, salt and pepper. Put them in the oven at about 180. Cook until peppers start to get a little browned and soft.
While the pepper are cooking, prepare the filling. You can really put whatever veggies and whatever grain and whatever cheese (or no cheese) that you want but here's what I do. Sauté in a pot onions, garlic, zucchini and a can of chick peas. Once veggies get a little soft add spices (I use pepper, garlic powder, cumin and paprika). Then add a cup of rice and the appropriate amount of water depending on what kind of rice you're using. Let it come to a boil and then Lower the flame. Cook until rice is ready. Shut off flame and stir in half a can of crushed tomatoes and a container of feta cheese.
Take peppers out of oven and stuff with filling. Pour the rest of the canned tomatoes on top and cook for another 20 or so minutes.