Preheat the Oven: Preheat your oven to 375°F (190°C).
Prepare the Crust: If using a pre-made pie crust, follow the package instructions for pre-baking. If making a homemade crust, blind bake it for about 10 minutes until lightly golden.
Saute Vegetables: In a saute pan, cook the chopped spinach, cherry tomatoes, and red onion until softened. Set aside to cool.
Whisk Eggs and Milk: In a mixing bowl, whisk together the eggs and whole milk until well combined. Season with salt and pepper.
Assemble the Quiche: Spread the sauteed vegetables evenly over the pre-baked crust. Sprinkle crumbled goat cheese on top. Pour the egg and milk blend evenly onto the vegetables and cheese.
Bake: Place the quiche in the preheated oven and bake for 25-30 minutes or until the center is set and the top is golden brown.
Garnish and Serve: Remove the quiche from the oven and let it cool for a few minutes. Garnish with fresh herbs. Slice and serve.