Preheat the oven to 350 degrees F.

Grease a 9-inch pie dish with cooking spray and press the pie dough evenly into the pie dish. Place a piece of parchment paper over the pie crust and weigh it down by placing some dried beans or pie weights in the center of the crust.

Place the pie dish with the crust onto a baking sheet and bake it on the middle rack of the oven for 12-15 minutes, until the crust is lightly golden brown. Remove and let cool for a few minutes.

Meanwhile, heat a medium skillet with olive oil and butter to medium heat. Once the pan is hot add the mushrooms, peppers, and onions. Toss and cook the veggies for 3-4 minutes until they are soft and the mushrooms are starting to brown. Then season them with some salt and pepper and some fresh thyme.

Toss in the spinach and cook until wilted, about 2 minutes. Remove the pan from the heat and let the veggies cool for a couple of minutes.

Add the eggs, milk, basil, garlic powder, and some salt and pepper to a large bowl and whisk until slightly frothy. Then stir in ⅓ cup of the cheese.

Spread the cooked veggies over the bottom of the pie crust.

Pour the egg mixture over the veggies and top evenly with the remaining shredded cheese.

Place the quiche on the baking sheet back into the oven and bake it for 45-50 minutes, until the eggs are set in the middle. Then remove it from the oven and let it cool for at least 15 minutes. Garnish with more fresh thyme before you slice and serve it.