1. 1. Saute the Chicken: Heat the olive oil in a large pot or Dutch oven over medium heat. Add the diced chicken pieces and cook for 5-7 minutes, stirring occasionally, until they are lightly browned and cooked through. Remove the chicken from the pot and set it aside on a plate.

2. 2. Soften the Aromatics: In the same pot, add the chopped onion and cook for 3-5 minutes until it becomes translucent and softened. Next, stir in the minced garlic and cook for another minute until fragrant. Be careful not to burn the garlic.

3. 3. Build the Broth: Pour in the chicken broth, scraping up any browned bits from the bottom of the pot with a wooden spoon. Stir in the dried oregano and black pepper. Bring the broth to a gentle boil.

4. 4. Cook the Orzo: Once the broth is boiling, add the orzo pasta. Reduce the heat to medium-low, cover the pot, and simmer for 8-10 minutes, or until the orzo is tender. Stir occasionally to prevent the pasta from sticking to the bottom of the pot.

5. 5. Combine and Finish: Return the cooked chicken to the pot. Stir in the fresh lemon juice and chopped spinach. Cook for another 2-3 minutes, or until the spinach has wilted completely.

6. 6. Season and Serve: Taste the soup and season with salt as needed. Ladle the hot soup into bowls and garnish with fresh chopped parsley, if desired.