For the Chimichurri:
1 In a bowl, combine the olive oil, vinegar, parsley, garlic, oregano, mint, red pepper flakes, salt and pepper. Stir to combine, taste for seasoning and adjust with salt or vinegar as desired. Cover and set aside at room temperature until ready to use.
For the Lemon Rosemary Chicken:
3 Half-spatchcock the chicken by cutting along one side of the backbone with a sharp knife or pair of kitchen shears. Place the chicken on a cutting board, breast-side up, and use your hands to flatten it. Pat the chicken dry with paper towel and transfer it to a roasting tray.
4 In a bowl, combine the olive oil, lemon zest, lemon juice, rosemary, garlic, salt, smoked paprika and black pepper and stir to combine. Pour the marinade overtop of the chicken and massage all over to evenly coat. Cover and refrigerate for 6 hours to overnight for best results.
5 Preheat your Traeger grill to 475F. If using a conventional grill, setup a two-zone medium-high heat. Using butcher’s twine, tie a handful of rosemary sprigs to the bottom of a wooden spoon to create a basting brush.
6 Reserve the marinade in the roasting tray and place the chicken, skin side-up, on the top rack of the Traeger. Add the potatoes, peppers and onions to the roasting tray and toss in the reserved marinade to coat. Position the tray directly beneath the chicken to catch the drippings. Roast the chicken until the skin is golden brown and the thickest part of the breast registers around 150F, around 40 minutes. Baste the skin with some of the chimichurri using the rosemary brush. The vegetables are ready when the potatoes are fork-tender.
7 Carefully flip the chicken over, baste with some more of the chimichurri, and cook the skin side until it is lightly charred and the thickest part of the breast registers 160F, around 10 more minutes. If using a conventional grill, place the chicken over direct and cook until the skin is lightly charred and the thickest part of the breast registers 160F, 5 to 10 more minutes.
8 Transfer the chicken to a cutting board, baste once more with some of the chimichurri, loosely tent with foil and let it rest at least 10 minutes before carving. Serve the chicken with the roasted vegetables and more chimichurri.
