Preheat oven to 190°C.
Beat eggs, milk and oil together.
Sift the flour, baking powder and salt together and add the milk mixture.
Stir until just mixed.
Add spinach, bacon, onion and pecorino to mixture and fold in lightly.
Spoon equal amounts of batter into a greased muffin pan and bake for 15 - 20 minutes or until muffins spring back when gently pressed.
Allow to cool slightly before turning out onto a wire rack. Serve warm with butter.