Nope! You will not need to pre cook the quinoa for this recipe. There will be plenty of moisture in the slow cooker as well as in the bell peppers that will help the quinoa cook. It is a small grain and absorbs lots of water, so it will become perfectly cooked the longer it is in the slow cooker. If you decide to use rice, you will want to cook the rice before adding it to your bell peppers, since it can take longer and will need to be fully submerged in the water to cook correctly.