Preheat oven to 375°F.

Roll out pie crust and place it in a 9-inch pie pan. Press gently to fit, and flute the edges if you like.

In a skillet over medium heat, add olive oil. Cook mushrooms for about 5 minutes until tender.

Add spinach to the skillet and stir until wilted, about 2 minutes.

In a large bowl, whisk together eggs, milk, salt, pepper, and garlic powder until combined.

Spread the spinach and mushrooms evenly in the pie crust.

Sprinkle shredded cheese over the vegetables.

Pour the egg mixture on top, making sure it spreads evenly.

Bake for 40 to 45 minutes, until the center is set and the top is golden.

Let cool for 5–10 minutes before slicing and serving.