How to Make It
In a large ziplock bag, combine buttermilk, garlic, 3/4 fresh thyme, lemon, 2 Tbsp. kosher salt, freshly ground pepper, and leg quarters. Seal the bag and use your hands to massage the chicken with the ingredients in the bag. Place bag in refrigerator for 8 to 24 hours.
One hour before baking, remove the bag from the refrigerator, take the chicken quarters out and pat them dry. Remove them to a plate where they can come to room temperature. Discard the bag and the marinade ingredients.
Preheat oven to 425°F. Place chicken quarters in a baking dish, brush with olive oil, and roast in the middle of the oven until the skin on the chicken is well browned, 50 to 55 minutes.
Remove pan from the oven and cover with aluminum foil, allowing the meat to rest for 20 minutes before serving.
Garnish chicken with remaining thyme leaves.
Under the leg quarters, consider placing thinly sliced potatoes, onion, fennel, carrots, or other vegetables that have been coated with olive oil and seasoned with salt before roasting. The juices rendered from the chicken will flavor the vegetables as they roast.