Grate the courgettes coarsely and place in a clean tea towel. Squeeze out as much moisture as you can - this is the key to crispy fritters.
Put the squeezed courgette in a bowl. Add the crumbled feta, spring onions, eggs, flour, oregano and a good grind of black pepper. Mix well.
Heat the oil in a large frying pan over medium heat. Drop tablespoons of the mixture into the pan and flatten slightly with the back of a spoon.
Cook for 3-4 minutes on each side until golden and crispy. You may need to do this in two batches.
Drain on kitchen paper. Mix the natural yoghurt with the lemon juice and a pinch of salt to make a quick dressing.
Serve the fritters warm with the lemon yoghurt drizzled over the top.