Place the chicken breasts in the slow cooker. Add the lemon juice, lemon zest, minced garlic, thyme, rosemary, chicken broth, salt, and pepper. Stir gently to coat the chicken.
Cover and cook on low for 6 hours or until the chicken reaches an internal temperature of 165°F.
About 20 minutes before the chicken is done, combine the quinoa with 2 cups water in a medium saucepan. Bring to a boil, then reduce to a simmer and cook for 15 minutes until the water is absorbed.
In the final 10 minutes of cooking, add the asparagus pieces directly to the slow cooker and stir to combine with the broth.
Remove the chicken from the slow cooker and slice or shred it. Fluff the quinoa with a fork, then divide the quinoa among four plates. Top each with chicken, asparagus, and a spoonful of the cooking broth. Finish with chopped parsley.