Preheat and prep the pan: Heat the oven to 425°F (220°C). Line a large sheet pan with parchment for easy cleanup, or lightly oil it.
Make the garlic marinade: In a bowl, whisk olive oil, minced garlic, lemon zest and juice, Dijon, honey, smoked paprika, oregano, red pepper flakes, 1 teaspoon salt, and 1/2 teaspoon black pepper.
Season the potatoes first: Toss the halved baby potatoes with 2 tablespoons of the marinade.
Spread on the sheet pan and roast for 10 minutes to give them a head start.
Prep the chicken: While the potatoes start roasting, pat the chicken dry. Toss with half of the remaining marinade until coated. Let it sit while you prep the veggies.
Season the veggies: In the same bowl, toss broccoli, bell pepper, and red onion with the last of the marinade.
Add a pinch more salt and pepper if needed.
Add everything to the pan: Pull the potatoes from the oven. Nestle the chicken pieces among them, then scatter the vegetables around in an even layer without crowding.
Roast until done: Return the pan to the oven and roast 18–22 minutes, flipping the veggies once. Chicken is done when it reaches 165°F (74°C) at the thickest part.
Broil for color (optional): For caramelized edges, broil on high for 2–3 minutes.
Watch closely to avoid burning the garlic.
Rest and garnish: Let the chicken rest 5 minutes. Sprinkle with chopped parsley and an extra squeeze of lemon for brightness.
Serve: Plate with pan juices spooned over the top. Add crusty bread, rice, or quinoa if you want a starch beyond the potatoes.