Heat a heavy-bottomed stockpot or Dutch Oven over medium-high heat. Pour in the olive oil and reheat for 30 seconds, then add the onions, carrots, celery, Tarragon, Thyme, and Rosemary. Sweat down for 10 minutes, stirring with a flat bottomed wooden spoon every few minutes.
Toss in the garlic + quartered lemon and cook until aromatic, about a minute.
Add the stock, roasted shredded chicken, orzo, and bring to a boil reduce the heat and simmer until the orzo is just tender about 10-15 minutes.
Remove quartered lemon. Season with salt and pepper to taste and mix in the lemon juice, zest. Ladle into warm bowls, garnish with fresh herbs, sliced lemon and serve with crusty bread and/or a side salad.