Prep your veggies by using a mandolin to slice carrots and celery. Using a mandolin will ensure that your soup will cook in under 30 minutes. Otherwise, unevenly sized veggies may cause the soup to take significantly longer to cook! Alternatively, you can dice them.
Melt butter or oil in a large stockpot or dutch oven over medium heat. Add onion, carrots, celery, and garlic. Cook, occasionally stirring, until tender, about 5-7 minutes.
Add chicken broth, bay leaves, salt, pepper, chicken, and quinoa. Bring to a boil, reduce the heat, and simmer, covered, until the chicken is cooked through and the quinoa is fluffy about 20-30 minutes.*
Remove the soup from heat and then remove the chicken, dice, and return to soup—salt and pepper soup to your final taste. Garnish with fresh parsley and lemon juice. Serve immediately.