Preheat broiler. In a large skillet, cook turkey and beef over medium heat until no longer pink, 5-7 minutes, breaking into crumbles; drain.
Prepare rice according to package directions. Add rice to meat mixture.
Cut peppers lengthwise in half; remove seeds. Place on a foil-lined 15x10x1-in. baking pan, cut side down. Broil 4 in. from heat until skins blister, about 5 minutes. With tongs, turn peppers.
Fill with turkey mixture; top with enchilada sauce and sprinkle with cheese. Broil until cheese is melted, 1-2 minutes longer. If desired, top with cilantro.