Bring 4 cups of olive oil to a simmer. Add 3 gloves of garlic, 1 tablespoon of crushed red pepper, and a dash of salt and pepper. Let mixture steep for 20 minutes, let cool, and filter out only the oil. Use to drizzle.
Put 3 cups quinoa in the pot and toast dry for 3-4 minutes. Add 6 cups cold water and bring to a boil. Whisk to avoid clumps. Once the water is boiling, remove from heat, cover with lid, and let sit for 15 to 20 minutes.
Sauté thinly sliced red onion until caramelized. Add the sliced mushrooms, sun-dried tomatoes, and spinach. Sauté together until soft. Portion out quinoa until bowls and top with sautéed veggies, crumbled feta cheese, and toasted walnuts. Drizzle with chile oil.