Heat the olive oil in a cast-iron skillet over low heat.

Add the garlic and cook for 1 minute, until fragrant.

Turn off the heat,add the spinach, and cover the skillet.

Let sit until the spinach is slightly wilted, 3 to 4 minutes.

Transfer to a bowl, add the quinoa, stir to combine, and set aside.

Continue with the instructions for the frittata, pouring the egg mixture into the skillet and omitting the cheese in the base recipe.

Before placing the frittata in the oven, sprinkle the spinach mixture and cheese over the eggs.