Warm the pot: Heat the olive oil in a large soup pot over medium heat. Add onion, carrots, and celery. Cook 5–6 minutes, stirring, until softened and fragrant.
Add aromatics: Stir in the garlic, salt, pepper, oregano, and bay leaf.
Cook 30–60 seconds until the garlic smells nutty, not burnt.
Build the base: Pour in the chicken broth. Bring to a gentle boil. If using uncooked brown rice or quinoa, add it now.
Cook the chicken: Nestle the chicken breasts or thighs into the hot broth.
Reduce to a steady simmer, cover, and cook 12–18 minutes, depending on thickness, until the chicken is cooked through.
Shred the chicken: Transfer the chicken to a plate and shred with two forks. Return the shredded chicken to the pot. If using pre-cooked grains, stir them in now.
Brighten it up: Turn off the heat.
Stir in the lemon zest and lemon juice. Start with 1/4 cup juice, then taste and add more if you like it zingier.
Add greens and herbs: Fold in spinach or kale and let it wilt for 1–2 minutes. Remove the bay leaf.
Stir in parsley or dill. Add a pinch of red pepper flakes if you want heat.
Taste and adjust: Add more salt, pepper, or lemon to balance the flavors. The broth should taste bright but not sour.
Serve: Ladle into bowls and enjoy warm.
A drizzle of olive oil or extra herbs on top is a nice touch.