Preheat the oven to 375°F (190°C).
Prepare the potato crust by greasing a pie pan with olive oil.
Layer the thinly sliced potatoes in the pie pan, overlapping them slightly.
Drizzle the potatoes with olive oil and sprinkle with salt and pepper.
Bake the potato crust for 25 minutes or until golden brown.
While the crust is baking, whisk together the eggs, milk, salt, pepper, and oregano in a bowl.
Remove the crust from the oven; layer the crumbled feta and sliced tomatoes on top of the crust.
Pour the egg mixture over the feta and tomatoes, ensuring an even distribution.
Return the quiche to the oven and bake for an additional 25-30 minutes, or until the filling is set.
Let the quiche cool for a few minutes before slicing and serving warm or at room temperature.