Char peppers over a gas flame or under a hot broiler, turning to blacken all over. Place in a paper bag, close tightly, and steam for 15 minutes. When cool enough to handle, rub off and remove blackened skin, taking care not to tear flesh. Cut a slit down the length of each, stopping about 1/2" from the tip. (If using bell peppers, simply cut off the top.) Scrape out ribs and seeds. Set aside.

Heat 2 tbsp. oil in a skillet over medium heat. Add onions and garlic and cook until soft and golden, about 20 minutes. Increase heat to medium-high, add beef and pork, breaking meat up with the back of a spoon, and brown for 7 - 10 minutes. Reduce heat to medium, season to taste with salt and pepper, and stir in tomatoes and nutmeg. Cook for 5 minutes, then remove from heat and stir in rice, marjoram, thyme, parsley, and 1 tbsp. oil. Adjust seasoning.

Preheat broiler. Spoon about 1/4 cup filling into each pepper and place on a cookie sheet. Sprinkle with bread crumbs, drizzle with remaining oil, and broil until golden. Serve hot or at room temperature.