In a bowl, whisk together the eggs, milk, salt, pepper, and garlic powder (if using) until well combined.
Heat the olive oil or butter in a non-stick skillet over medium heat.
Add the chopped spinach to the skillet and sauté for about 1-2 minutes until wilted.
Pour the egg mixture into the skillet with the spinach.
Gently stir the eggs with a spatula, allowing them to cook evenly.
When the eggs are nearly set but still slightly runny, sprinkle the feta cheese over the top.
Continue to cook for another minute until the eggs are fully cooked and the feta is warmed through.
Remove from heat and serve immediately.