Preheat your oven to 400°F (200°C).
Grease a large baking sheet with cooking spray or olive oil.
In a large bowl, whisk together the eggs and milk.
Add salt and pepper to taste.
Spread the diced potatoes evenly on the baking sheet.
Bake the potatoes for 10 minutes until slightly tender.
Remove from the oven and add the diced bell peppers and spinach.
Pour the egg mixture evenly over the vegetables.
Sprinkle shredded cheese on top.
Bake for an additional 15-20 minutes or until eggs are set.
Allow to cool slightly, then cut into squares.
Garnish with fresh herbs before serving.