To the slow cooker, add the quinoa, enchilada sauce, black beans, tomatoes, corn, red bell pepper, green bell pepper, chili powder, cumin, garlic powder, and 1/2 cup water. Stir to combine, then cover and cook on high for 2 1/2 to 3 hours or low for 5 to 6 hours, until the liquid is absorbed and the quinoa is tender.