Heat 2 teaspoons of olive oil in a large pot over medium-high heat. Add in the chicken and oregano and season with salt and pepper. Cook the chicken until lightly browned, but don't cook all the way through, about 3-4 minutes.

Remove the chicken from the pot onto a plate. Add the remaining 2 teaspoons of olive oil to the pot along with the onion, carrots, celery, rosemary, thyme and red pepper flakes. Season with salt and pepper. Sauté until the vegetables are tender, 3-4 minutes and then add in the garlic. Sauté another 30 seconds.

Add the broth to the pot, stir and bring to a boil over high heat. Once boiling, add in the orzo and reduce the heat to a simmer. Cook for 5 minutes and then add in the spinach, chicken and dill. Cook for another 5-7 minutes or until the orzo is tender and the chicken is cooked through.

Remove from the heat and discard the bay leaf. Stir in the lemon zest and juice. Taste for seasoning and add salt and pepper as needed.