Heat the olive oil in a large saucepan set over medium heat.
Add the onions, carrot and celery. Cook, stirring occasionally, until the onion softens and becomes translucent.
Add the garlic, thyme, rosemary, sage, salt and pepper. Cook, stirring, for 1 minute.
Pour in the chicken broth and stir in the brown rice. Bring the broth to a boil, then reduce the heat so that the liquid is at a lively simmer. On my stove, that’s between medium-low and medium, but varies from stove to stove.
Cover the saucepan. While cooking, stir the soup occasionally, scraping gently along the bottom of the saucepan with a wooden spoon, to make sure the rice isn’t sticking. Cook until the rice is tender, about 45 minutes. This will vary, depending on the rice and stovetop heat. Tasting the rice (careful, it will be hot) is the best way to test for doneness.
Remove the soup from the heat and stir in the turkey and parsley. Taste and adjust the seasoning, if necessary.
Add additional broth if too much of it cooked down while simmering.