Set oven to 400F.
Beat together with Greek yogurt (or milk) then toss in seasonings. Mix together.
Add the quinoa, veggies and cheddar to the egg mixture and mix thoroughly together using a spatula. Once mixed, you can add optional flour to the egg mixture in order to thicken it.
Evenly divide the egg mixture among the muffin molds. Bake in the oven for about 30 minutes at 400F, or until the egg mixture is fully cooked.
After baking, allow the frittatas to slightly cool before removing them from the muffin molds.