Preheat your oven to 350 degrees.
Take your pie shell out of the freezer, and let thaw. Place on preheating oven, to help speed up the process.
Chop up your vegetables (including the spinach) and heat on a large skillet on the stove over medium heat.
Add olive oil, minced garlic, and vegetables. Sauté until the peppers are soft and the spinach has wilted.
Remove the sautéed veggies from the heat, and let cool until at room temperature. Be sure not to mix anything that is too hot with raw eggs.
When cooled, add the veggies to the thawed pie shell and place on a baking tray. Carefully pour the egg whites over the veggie mix.
Cook for 30 minutes, then shut the oven off and keep the quiche in the cooling oven for another 15 minutes or until middle is set.