Heat the vegetable oil in a non-stick frying pan. Add the courgette and tomatoes and cook on the hob for 3-4 minutes, stirring often, until soft. Spread out over the base of the frying pan.
If you use a good non-stick frying pan the frittata will be easy to remove.
Beat the eggs and milk together and pour into the frying pan. Cook over a medium-low heat for 4-5 minutes to set the base, then transfer to the grill to set the surface - about 2-3 minutes. Remove from the heat and let the frittata cool for 3-4 minutes.
Take care not to cook over a high heat, or else the base could brown too much before the middle of the frittata is cooked.
Toast the slices of bread. Slice the frittata into wedges and serve with the toast.
You could also make the recipe with extra vegetables, such as mushrooms, spring onions and chopped peppers.