Preheat the oven to 350°F.

Spray a 9-inch pie plate liberally with nonstick cooking spray and transfer to a baking sheet.

Finely dice the scallion and set aside. Finely dice the red bell pepper and place in a large skillet. Add the baby spinach to the skillet.

Set the skillet over medium high heat and add the water. Cook the spinach and bell pepper, stirring frequently, until the spinach is fully wilted, the peppers are tender, and the water is completely evaporated. Set aside.

In a large mixing bowl, whisk together the eggs, egg whites, milk, Greek yogurt, scallion, garlic powder, salt, and black pepper until smooth.

Add the vegetables and cheeses to the egg and milk mixture. Fold with a rubber spatula until evenly distributed.

Pour the egg, vegetable, and cheese mixture into the prepared pie plate.

Bake the quiche on bottom rack of oven until the top is firm and lightly golden brown, 40-50 minutes.

Check to see that quiche is done. Remove from oven or add time as needed.

Allow to cool for at least 30 minutes at room temperature before slicing and serving. Leftover quiche may be stored covered in the refrigerator for up to 3 days.