Step 1: Preheat and Prep the Pan
Position one oven rack in the lower third and another in the upper third of your oven. Preheat the oven to 425°F (220°C). This high temperature is crucial for achieving caramelization without steaming the vegetables. Take a large, rimmed baking sheet (a standard half-sheet pan, 18″x13″). For easier cleanup and to prevent sticking, you can line it with parchment paper or a silicone baking mat. However, for maximum browning and fond development, roasting directly on the lightly oiled pan is best.

Step 2: Season the Chicken
Pat the chicken pieces completely dry with paper towels. This is a non-negotiable step for achieving crispy skin (if using) and proper browning. In a small bowl, combine 1 teaspoon of garlic powder, 1 teaspoon of smoked paprika, 1 teaspoon of dried oregano, and 1/2 teaspoon each of kosher salt and black pepper. Drizzle the chicken with 1 tablespoon of olive oil, rubbing it all over. Evenly sprinkle the spice mix over the chicken, rubbing it into all surfaces, including under the skin if applicable. Set the seasoned chicken aside at room temperature while you chop the vegetables.

Step 3: Chop and Season the Vegetables
Wash and dry all vegetables thoroughly. Cut them into uniform, bite-sized pieces. The goal is to have everything roast evenly. The potatoes and carrots are the densest, so they should be cut slightly smaller than the softer zucchini and broccoli. Place all the chopped vegetables (potatoes, carrots, bell pepper, onion, broccoli, zucchini, and smashed garlic cloves) in a large mixing bowl. Drizzle with the remaining 2 tablespoons of olive oil. Sprinkle with 1 teaspoon of kosher salt and 1/2 teaspoon of black pepper. Toss vigorously with your hands or two large spoons until every piece is glistening and evenly coated with oil and seasoning.

Step 4: Strategic Arrangement on the Pan
This step ensures everything cooks perfectly. Spread the seasoned vegetables onto the prepared baking sheet in a single, even layer. It’s okay if they touch, but avoid piling them on top of each other, as this will cause them to steam rather than roast. Now, nestle the seasoned chicken pieces on top of and among the vegetables, skin-side up. Try to place the chicken on top of the denser vegetables like potatoes and carrots, as they can handle the longer cooking time and the chicken’s drippings.

Step 5: The Two-Stage Roast
Place the loaded sheet pan on the lower oven rack. Roast for 20 minutes. After 20 minutes, the vegetables will have started to soften and brown, and the chicken will be on its way. Now, move the pan to the upper rack. If you have convection, you can turn it on now. This move increases direct heat from the top, helping to crisp the chicken skin and finish the roasting. Continue to roast for another 15-20 minutes. The total cooking time will be 35-40 minutes.

Step 6: Check for Doneness
The dinner is ready when the chicken is cooked through and the vegetables are tender and caramelized. For chicken thighs, the internal temperature should register 175°F (80°C) in the thickest part (they remain juicy at this temp). For chicken breasts, aim for 165°F (74°C). The potatoes and carrots should be easily pierced with a fork, and the broccoli and peppers should have some charred, crispy edges. The onions will be soft and sweet.

Step 7: Rest and Garnish
Remove the pan from the oven. Using tongs, transfer the chicken pieces to a clean plate or cutting board and let them rest for 5 minutes. This allows the juices to redistribute, ensuring moist meat. While the chicken rests, you can give the vegetables a final toss on the pan, scraping up any delicious browned bits. Transfer the vegetables to a serving platter or serve directly from the pan for a rustic presentation. Place the rested chicken atop the vegetables. Garnish with fresh chopped parsley and a sprinkle of lemon zest. Serve immediately with lemon wedges on the side for a bright, fresh finish.