Prep. Preheat the oven to 350˚F. Heat the oil in a large, heavy-based pot or Dutch oven with a lid that’s about 7 qt or bigger. Make sure that the pot you use is safe to use in the oven and on the stovetop.
Season the chicken. Pat the chicken dry with paper towels. Then, spray the chicken with cooking oil and season it with the thyme, salt, basil, and lemon pepper.
Brown the chicken. Place the chicken in the heated oil, breast side down, and cook over medium-high heat for about 3 to 4 minutes, or until golden; turn it over and cook for 3 more minutes.
Add the aromatics and vegetables. Decrease the heat to low; add in the garlic and cook for 15 seconds. Add more oil, if needed. Scatter the onions, carrots, leeks, and lemons around the chicken; season the veggies with salt and pepper, then give them a stir. Cook for 2 minutes.
Add the broth and bring to a boil. Pour in about 5 to 6 cups of chicken broth, or just enough to come up about ¾ of the way up, but do not cover the entire chicken with liquid, especially not the breast part. Increase the heat to High and bring to a boil.
Roast in the oven. Once boiling, cover with the lid and cook in the oven for 1 hour and 15 minutes.
Add the orzo and continue to cook. Take the pot out of the oven. Carefully remove the lid; stir in the orzo. Put the lid back on and continue to cook in the oven for 30 more minutes.
Let it rest. Take the pot out of the oven, remove the lid, stir the orzo, and let it all rest for 15 minutes.
Serve. Remove the lemon wedges and toss them out, garnish the chicken, veggies, and orzo with parsley, and serve.