As Dr. Dressler writes in this article, cooked, white Quinoa can be used, in some cases, as a substitute for steel-cut oats or brown rice in the Dog Cancer Diet.
He writes that he doesn't recommend feeding quinoa to dogs that are in good condition or actively struggling with cancer cachexia. Don’t choose quinoa if your dog doesn’t want to eat. But if your dog is obese or overweight, it might be helpful. If your dog has oxalate kidney stones, he recommends that you should certainly avoid quinoa.
If you would like to use quinoa as your carbohydrate source, use white quinoa and then take the amount of oatmeal in the Dog Cancer Diet recipe and multiply it 3.5 times.
Please check with your veterinarian before making any changes to your dog's health care :-)