In a small blender or food processor, combine 1/2 cup cranberries, chopped oranges, 1/4 cup balsamic vinegar, extra virgin olive oil (EVOO), oregano, thyme, pepper, and salt. Blend until smooth.
Place the chicken thighs in a large sealable container or bag. Pour the marinade over the thighs, then seal and chill for at least one hour or overnight.
Preheat the oven to 375°F (190°C). Remove the chicken thighs from the marinade and place face down in a roasting pan. Discard the remaining marinade.
Place a sliced, intact ring of sweet onion on top of each chicken thigh. Generously drizzle on some EVOO and season with additional salt and pepper, to taste. Spread the rest of the cranberries between the chicken thighs.
Bake the dish in the oven for 25 minutes. Remove from the oven and turn the broiler on high. While the broiler heats up, flip the chicken thighs so that the onion is under the thighs and the skin side is facing up. Keep a watchful eye as you broil the chicken for another 5-10 minutes, until the chicken skin begins to bubble and char slightly.
Serve the cooked chicken thighs topped with the roasted sweet onion, a drizzle of the remaining balsamic vinegar, a fresh squeeze of orange, and a touch of cranberry relish, if desired. Serve with wild rice and broccoli as sides.