Preheat oven at 400 degrees Fahrenheit (200 degrees Celsius).
Brush some olive oil in a casserole dish or other dish about 8 x 10 inches.
In a large bowl mix the potatoes with the olive oil and oregano.
Place one layer of potatoes, sprinkle with a bit of salt and pepper and half of the feta.
Place a second layer of potatoes repeating the sprinkling with feta, salt and pepper.
Finish with a final layer of potatoes.
Take about ½ cup of hot water and mix it with the lemon juice and pour it in the corner of the dish. Tilt so the water spreads in the whole bottom of the pan (the water should be enough to cover the bottom potato layer).
Cover pan with aluminum foil with a few slits, and bake for about 10 minutes (with the fan).
After 10 minutes have passed, lower the heat to 320 degrees Fahrenheit (160 Celsius) and bake for about 1 hour, checking to make sure that the potatoes are cooked all the way through (check with a fork-it should easily pierce the potatoes).
Remove foil and bake uncovered for about 10-15 minutes to brown. Do not over-bake there should be a bit of water left on the bottom.
Sprinkle with parsley and serve.