Mix cauliflower, ham, egg, Cheddar cheese, flour, green onions, oil, and pepper together in a large bowl until evenly combined.

Set waffle iron to the highest heat setting and spray both griddles with nonstick spray. Spoon 1 cup of the cauliflower mixture into the center of the waffle iron. Keep the rest of the batter refrigerated. Close lid and cook for 10 minutes. Gently remove the waffle using a spatula and fork. Cook remaining batter.