Let's cook.
Preheat your oven to 375°F (190°C). Lightly grease a 6-cup muffin tin with olive oil or cooking spray.
In a medium bowl, whisk together the eggs, milk, dried oregano, salt, and black pepper until well combined.
Stir in the chopped fresh spinach and crumbled feta cheese into the egg mixture.
Evenly divide the egg mixture among the 6 muffin cups, filling each about two-thirds full.
Bake for 18-22 minutes, or until the egg muffins are set and lightly golden brown on top. A knife inserted into the center should come out clean.
Remove the muffin tin from the oven and let the egg muffins cool in the tin for 5 minutes before carefully removing them.
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