MIREPOIX: Add olive oil to a large pot over medium heat. Once the oil is shimmering, add in onion, celery, and carrots. Cook until the onion is translucent and veggies are crisp-tender, stirring occasionally, for about 7-9 minutes (Reduce heat if veggies are browning too quickly) Add in the garlic and stir for 30 seconds. While veggies are cooking, measure out all the spices.
SEASON: Add in the spices (chicken bouillon powder, salt, pepper, parsley, oregano, thyme, and Italian seasoning) and stir for 30 seconds. Add the chicken broth and bay leaf and increase heat to a boil. Once boiling, add in the orzo pasta. Cook according to package directions, subtracting 2 minutes from what the package cooking time says.
CHICKEN/SPINACH: Stir in the shredded rotisserie chicken and then spinach. Gently stir to warm through chicken and allow spinach to wilt, about 2-3 minutes. Remove from the heat. Stir in the lemon zest and juice. Season to taste if any additional salt/pepper is needed.
SERVE: Ladle into bowls and garnish, if desired, with fresh thyme. Add optional Parmesan cheese to individual bowls. Serve with crusty bread.