Season chicken thighs with salt and pepper, to taste.
Heat 1 tablespoon olive oil in a large stockpot or Dutch oven over medium heat. Add chicken to the stockpot and cook until golden, about 2-3 minutes; set aside.
Add remaining 1 tablespoon oil to the stockpot. Add garlic, onion, carrots and celery. Cook, stirring occasionally, until tender, about 3-4 minutes. Stir in thyme until fragrant, about 1 minute.
Whisk in chicken stock, bay leaves and 1 cup water; bring to a boil.
Stir in orzo, rosemary and chicken; reduce heat and simmer until orzo is tender, about 10-12 minutes.
Stir in lemon juice and parsley; season with salt and pepper, to taste.