Preheat your oven to 375°F (190°C).

In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add finely chopped onion and minced garlic, cooking for 3-4 minutes until translucent. Stir in diced bell peppers, zucchini, and roughly chopped spinach, seasoning with salt, black pepper, and dried thyme. Cook for 5-7 minutes until vegetables are softened.

In a mixing bowl, whisk together the eggs and almond milk until fully combined and frothy. If using nutritional yeast, mix it in now.

Once the sautéed vegetables have cooled slightly, add them to the egg mixture and gently fold until evenly coated.

Grease a 9-inch pie dish with olive oil. Pour the vegetable and egg mixture into the dish, spreading evenly.

Bake in the preheated oven for 30-35 minutes. Check for doneness by inserting a toothpick into the center; it should come out clean.

Remove the quiche from the oven and let it cool for about 10 minutes before slicing and serving.