01 - Preheat oven to 375°F. Lightly grease a 9-inch pie dish with cooking spray or olive oil.
02 - Evenly distribute spinach, cherry tomatoes, bell pepper, and red onion in the bottom of the prepared pie dish.
03 - Whisk together eggs, milk, salt, pepper, dried thyme, and garlic powder in a medium bowl until fully combined.
04 - Pour the egg mixture evenly over the arranged vegetables.
05 - Sprinkle cheddar and feta cheese uniformly over the top.
06 - Bake for 35 to 40 minutes until set in the center and lightly golden on top.
07 - Let cool for 5 minutes before slicing. Serve warm or at room temperature.