Preheat oven to 375°F.
In a large skillet, heat olive oil over medium heat. Add onion and garlic and cook until onion is translucent, about 5 minutes.
Add spinach to the skillet and cook until wilted, about 3 minutes.
In a separate bowl, whisk together eggs, milk, feta cheese, salt, and black pepper.
Place the pie crust in a 9-inch pie dish. Pour the spinach mixture into the pie crust.
Pour the egg mixture over the spinach mixture.
Bake for 35-40 minutes, or until the quiche is set and the crust is golden brown.
Let the quiche cool for a few minutes before slicing and serving.
Enjoy your delicious and creative Spinach and Feta Quiche!