Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.
Place the ground beef into a skillet over medium heat, and brown the meat, breaking it apart into crumbles as it cooks, about 8 minutes.
Drain excess fat. Stir in the taco seasoning, water, chili powder, cooked rice, salt, garlic salt, black pepper, and 1 can of tomato sauce; mix until thoroughly combined. Bring to a boil, reduce heat to low, and simmer 20 minutes.
Meanwhile, cut the bell peppers in half lengthwise, and remove stems, membranes, cores, and seeds.
Place a steamer insert into a large saucepan, and fill with water to just below the bottom of the steamer. Cover, and bring the water to a boil over high heat.
Place the peppers into the steamer insert, cover the pan, and steam until just tender, 3 to 5 minutes.
Place the steamed peppers into the prepared baking dish, and fill lightly with the meat filling. Press 1 cube of Colby-Jack cheese into the center of the filling in each pepper, and spoon the remaining can of tomato sauce over the peppers. Cover the dish with aluminum foil.
Bake in the preheated oven until the peppers are tender and the filling is hot, 25 to 30 minutes.
