Melt butter with oil over medium-high heat in a large Dutch oven. Sauté the celery, carrots, and onions for 5-7 minutes.
Stir in the garlic and cook for about 30 seconds.
Pour the chicken broth into the pot. Add the Italian seasoning and chicken. Bring the chicken soup to a boil.
Cover the Dutch oven with a lid (slightly open on the side), reduce the heat, and simmer the chicken soup for 15 minutes.
Remove the lid, stir the orzo into the soup, and cook for another 10 minutes until the orzo is cooked through. Stir regularly to avoid the pasta sticking to the bottom of the pot.
Take the cooked chicken breasts out of the pot and shred with two forks, then add it back in.
Add the lemon juice and parsley and adjust the seasoning with salt and pepper, as needed. Sprinkle with parmesan and serve the lemon chicken orzo soup immediately. Enjoy!
