Heat 2 tablespoons of olive oil in a large non-stick skillet over medium-high heat. Add potatoes and cook for 6 to 8 minutes, or until softened and begin to brown. Remove from the pan and set aside.
Add the remaining olive oil to the pan and add onions and red pepper. Cook for about 6 minutes, or until the vegetables are soft and the onions are translucent. Season with salt and pepper.
Add spinach and garlic to the pan and cook until the spinach is wilted and the garlic is fragrant for about one minute. Season with salt and pepper. Remove from heat.
Whisk eggs and milk together until smooth. Add salt and pepper.
Add the reserved potatoes back to the pan. Spread the vegetables evenly in the pan. Pour the egg mixture over the vegetables. Add the cheese to the top, reserve some for after it is baked.
Bake until set, about 15 minutes. You do not want to overcook the eggs.
Let sit for 5 minutes in the pan and transfer to a plate. Garnish with chopped basil and reserved cheese.