This is what I make when there's a craving for stuffed peppers. My family absolutely loves this. I generally don't use salt in this recipe, I think there's plenty of saltiness from the olives and canned tomatoes, but your preferences may vary.
Start boiling the water for the rice according to package directions. ( I use the same water for the peppers, but of course you don't really have to) Add the rice, and during last 5 minutes of boiling, add the largely chopped peppers. Cook until rice is done and peppers are done to your liking. (You can always remove the peppers with a slotted spoon so they don't get too done for your taste)
In a large fry pan, brown the ground beef and onion together. Drain and add remaining ingredients except for the cheese. Add rice and peppers, mix in and heat through. Add the cheese and mix until melted. Serve.