Preheat the oven to 375 degrees F (190 degrees C).
Place turkey and beef in a large bowl. Add onion, carrot, spinach, egg, taco seasoning, garlic, pepper, and ketchup. Mix with your hands until blended. Shape into 3 equal-sized loaves and place into a 9×13-inch baking dish.
Bake in the preheated oven until no longer pink in the center, about 1 1/2 hours. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).