1. Preheat the oven to 400° F.
2. Cut lemons into fourths. Insert one cut lemon into the cavity of each chicken and add a generous sprig of thyme to each. Set aside.
3. Make the oil - Strip the leaves from the remaining thyme stalks and place in food processor. Add garlic, olive oil, juice of 1/2 lemon, salt and pepper. Blend together. It should be quite liquid.
4. Spoon the oil mixture all over the chickens, working it into all the crevices. Then place the chickens in a roasting pan, breasts down, and pour any remaining oil over the chickens.
5. Cover the chickens loosely with foil and roast in the oven for 30 minutes. After 30 minutes, remove the foil and roast for another 20-30 minutes at the same temperature. After the additional 30 minutes, reduce the temperature to 350° F and cook for approximately 15 more minutes. Chickens are fully cooked when the juices run clear and the temperature reads 160° F. Turn off the oven and let the birds rest in the residual heat for at least ten minutes. Remove from the oven, carve.
Note: Pan juices can be served as is with the chicken or made into a simple gravy.