Preheat oven to 400° Prepare rice in small saucepan according to package instructions & heat oil in large skillet over medium heat.
Trim the tops off each bell pepper and remove seeds and membrane from inside. Place the bell peppers into the prepared pan.
Cook onion for 5 minutes in saucepan or until soft. Stir in tomato paste abd garlic and cook for about 1 minute or until fragrant.
Add ground beef and cook, break up meat with wooden spoon until no longer pink, 6 mintues. Drain fat.
Return beef mixture to skillet, then stir in cooked rice and diced tomatoes. Season with oregano, salt, and pepper. Let simmer until liquid has reduced slightly, about 5 minutes.
Place peppers cut side-up in a 9"-x-13" baking dish and drizzle with oil.
Spoon beef mixture into each pepper and top with Monterey jack, then cover baking dish with foil until peppers are tender, about 35 minutes. Uncover and bake until cheese is bubbly, 10 minutes more.
Garnish with parsley before serving.
