Preheat oven to 375°F (190°C).
Combine the flour and salt into a bowl and rub in the margarine. Mix in the porridge oats until blended then and add water to make dough. Press dough into a 9” deep dish pie plate. Chill for 1 hr or overnight.
The dough can be made and frozen for use at a later date.
Heat the oil in a pan and sauté the onion gently until transparent. Pour into pie plate add the ¾ cup of cheese, ham and spinach.
Beat the eggs, milk and pepper then pour over the onion mixture. Stir together lightly. Sprinkle the reserved ¼ cup cheddar cheese and parmesan cheese (if using) on top.
Bake at 375° for 1 hour or until golden on top and tooth pick comes out clean. Remove from oven and let set for 10 min before serving.