Lightly beat Eggs, Milk, Flour and Baking Powder together. Season with Salt & Pepper.
Preheat the grill.
Heat Oil in a non-stick fry-pan and fry Vegetables until lightly coloured.
Turn heat down and add the egg mixture. Stir to coat the Vegetables.
Leave on the low heat for about 10 mins for it to set on the base.
Then place under the grill (cover handle with foil if necessary) for a further 10 mins until the Frittata is cooked though.
Remove from grill and use a spatula to loosen the sides. Slide on to a plate.