Heat oil in a pan, fry the bacon until lightly brown, then add the onion and mix again. Add the spinach then transfer it in a bowl. In the same bowl, add the bell pepper, tomato, then mix well and set aside.
Preheat the oven to 200 degrees F.
Beat all eggs in a bowl, then pour the milk and season it with salt and ground black pepper. Mix well.
Place all the sliced potatoes in the rectangular baking pot, then pour the mixture and beaten egg mixture into the baking pot.
Top it with parmesan cheese, and bake it for 30 minutes.
After 30 minutes, serve hot and enjoy!