Preheat your sous vide machine to 148 degrees Fahrenheit.
While the sous vide bath preheats, rinse the whole chicken under cold water and discard any extra pieces.
Place the whole chicken breast side down on a cutting board. Use sharp kitchen shears to cut along the backbone and remove it. Save for stock if desired.
Flatten the chicken to promote even cooking.
Season both sides with salt and pepper, then add garlic and oregano on the skin side.
Transfer the chicken to a large sous vide bag with three slices of orange, and vacuum seal.
Cook the chicken in the sous vide bath for six hours.
Shock the bag in an ice bath for five to ten minutes after cooking.
Set your oven broiler to high. Remove the chicken from the vacuum bag, pat it dry.
Place the chicken on a rack over a baking sheet, drizzle with butter, and broil for three to eight minutes.
Remove when golden brown and let rest for 15 to 30 minutes.
Garnish with fresh parsley and remaining orange slices before serving.
