Preheat the oven to 350 degrees F (175 degrees C). Grease a loaf pan.
Mix eggs, spinach, mushrooms, bread crumbs, onion, milk, blue cheese, Worcestershire sauce, garlic, cayenne pepper, oregano, basil, salt, and black pepper together in a large bowl. Add ground beef and mix thoroughly with your hands; pack into the prepared loaf pan.
Bake in the preheated oven until no longer pink in the center, 45 to 60 minutes. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).