In a small food processor, combine oregano, lemon zest, lemon juice and garlic. Pulse a few times until it looks like pesto. Add olive oil, salt and pepper and pulse to combine.
Using your hands, rub lemon-oregano marinade all over chicken. Using your fingers, gently lift the skin on either side of the neck and rub plenty of marinade directly onto the breast meat, under the skin. Don't forget to get some inside the cavity (where the organs were).
(optional) Truss your bird if desired. Elise has a helpful step-by-step photo tutorial on how to truss a chicken. Why truss? It's basically for looks, and brings the legs together nicely. I do not bother to truss my birds, but do admire how the end product of a trussed roast chicken looks. It's up to you.
Refrigerate for 2-8 hours to allow the marinade to infuse the meat. Remove from fridge about an hour before cooking.
Preheat oven to 450°F.
Place chicken in roasting pan breast side up (I like to use a clay baker for roasting fowl, but unfortunately mine broke during our move last winter!) and place in oven. Roast for ten minutes.
Reduce heat to 400°F and roast about 1 hour and 45 minutes, checking for doneness after 1 1/4 hours.
Remove from oven, cover loosely with aluminum foil and let stand 20 minutes before slicing.