Step 1

Combine 8 cups water, oranges, lemons, chiles, parsley, thyme, bay leaves, rosemary, garlic, salt, and peppercorns in a large stockpot. Bring to a boil over high. Cook, whisking occasionally, until salt dissolves and herbs are aromatic, about 2 minutes. Remove from heat; let cool completely, about 1 hour. Place chicken halves in mixture in stockpot. (Chicken should be fully submerged in liquid.) Cover and refrigerate 24 hours.

Step 2

Process all chimichurri ingredients in a blender or food processor until smooth, about 1 minute, stopping to scrape down sides as needed. Store in refrigerator in an airtight container until ready to use, up to 8 hours.

Step 3

Process all chimichurri ingredients in a blender or food processor until smooth, about 1 minute, stopping to scrape down sides as needed. Store in refrigerator in an airtight container until ready to use, up to 8 hours.

Step 4

Stir together all spice blend ingredients in a small bowl until combined. Set aside.

Step 5

Open bottom vent of a charcoal grill completely. Light 2 charcoal chimney starters filled with hardwood lump charcoal. When coals are hot, pour them evenly onto the 2 outer sides of grill, leaving center of grill unlit. Top each side of coals with an oak wood chunk. Adjust vents as needed to maintain an internal temperature of 300°F to 350°F. Coat top grate with oil; place on grill. (If using a gas grill, preheat to medium-low [300°F to 350°F] on outer burners, leaving middle burner[s] unlit.) Remove chicken from brine; discard brine, and pat chicken dry.

Step 6

Place chicken, skin side up, on oiled grates over center portion of grill without coals (or unlit center portion of gas grill). Grill, uncovered, until a thermometer inserted in thickest portion of breasts registers 110°F, about 15 minutes, rotating chicken every 2 to 3 minutes to avoid burning. Flip chicken on grates; grill until skin is slightly caramelized and browned, about 3 minutes. Cover and grill until a thermometer inserted in thickest portion of breasts registers 150°F, about 25 minutes, flipping and rotating chicken every 5 minutes.

Step 7

Sprinkle chicken all over with 2 tablespoons spice blend. Place chicken, skin side up, on grates. Grill, uncovered, until a thermometer inserted in thickest portion of breasts registers 155°F, 40 to 45 minutes. Remove chicken from grill, and cover loosely with aluminum foil. Let rest 15 minutes. Carve chicken. Sprinkle with additional spice blend to taste. Serve with chimichurri.