1. Turn the oven to 400°F and let it preheat. Next, clean out the cavity of the Cornish hens and insert half a lemon and three thyme sprigs in each space.
2. Loosen the skin from the breasts carefully so as not to tear it off. Then, insert the thyme and parsley under the loose skin. Rub olive oil over the hens and season with salt and pepper.
3. Set the hens on a roasting pan and toss in the oven. Cook for up to 45 minutes until the juice runs clear. Also, make sure the thickest part (thigh, mostly) reads 145 to 180°F on the thermometer.
4. Once it’s ready, take the hens out and leave them to sit for 10 minutes. Then, serve with thyme sprigs as garnish.

Also, check out this fantastic video recipe for more information about cooking Cornish hens at 400°F.