I cooked this a few Saturdays ago. I bought two whole chickens, removed the backbones and rubbed them down with fresh garlic, fresh lemon juice, kosher salt and fresh-ground black pepper. I let them rest in the fridge for four hours.
Then I lit my gas grill (yes, I know I am going against my purist view by using gas instead of charcoal, but you try fitting two whole split birds on my tiny charcoal grill/smoker), and over medium-high heat, placed oiled whole, split garlic and rosemary sprigs. I reduced the heat to medium, and placed the prepared chicken on top of the aromatics.
I cooked the birds over the slow-burning garlic and rosemary for about 40 minutes, until the thighs “temped” at 160. The carryover cooking took it beyond 165, so don’t worry about under-cooking. I then charred green onions, and once the chicken had rested at least 10 minutes, I carved and we devoured.