Make the lemon-herb marinade: In a mixing bowl whisk together 4 tbsp fresh lemon juice, 2 tbsp olive oil (from the 4 tbsp total), minced garlic, chopped rosemary and thyme, 1 tsp salt and 1/2 tsp freshly cracked black pepper. The acid (lemon) will lightly tenderize and flavor the chicken while the oil carries fat-soluble aromatics and helps develop color during grilling.

Marinate the chicken: Pat the 600 g chicken thighs dry with paper towels (removes surface moisture so they sear better), then add them to the marinade and turn to coat. Cover and refrigerate for 30–60 minutes (no more than 2 hours). Short acidic marinades keep the meat tender — long marinades can make the texture mealy.

Preheat and prep: Preheat oven to 425°F (220°C). If using a grill, preheat to medium-high and oil the grates. Line a large rimmed baking sheet with foil and set a cooling rack on it (rack keeps vegetables out of pooled oil so they roast and caramelize). Meanwhile rinse the quinoa in a fine sieve under cold water for 20–30 seconds to remove bitter saponins; drain well.

Cut and dress the vegetables: Toss Brussels sprouts (320 g), carrot batons (240 g), thinly sliced fennel (120 g) and sliced beets (240 g) with the remaining 2 tbsp olive oil, 1 tsp smoked paprika, 1 tsp salt and 1/2 tsp black pepper. Arrange them in a single layer on the prepared sheet tray. Even spacing helps them roast evenly and develop deep caramelized edges.

Roast the vegetables: Roast on the middle rack for 22–28 minutes, tossing halfway through. Roast until sprouts are browned at the edges and carrots are tender — Maillard browning concentrates natural sugars for a sweet, nutty flavor. If beets are already roasted/precooked, add them in the last 8–10 minutes so they warm through without drying out.

Cook the quinoa: While the veg roasts, bring 480 ml water (or low-sodium stock) to a boil in a medium saucepan. Add a pinch of salt and the rinsed quinoa (240 g). Reduce to a simmer, cover and cook for 12–15 minutes until water is absorbed. Remove from heat and let sit covered for 5 minutes — that rest steams the grains so they fluff instead of collapsing.

Finish the quinoa: Fluff the quinoa with a fork (this separates grains and keeps it light). Immediately fold in the 80 g baby spinach so residual heat wilts it gently and brightens the quinoa, plus fold in 2 tbsp chopped parsley and a pinch of salt and pepper to taste. The warm spinach adds color and micronutrients without additional cooking time.

Cook the chicken: Heat a large cast-iron skillet or grill pan over medium-high heat until smoking lightly (this hot surface gives an immediate sear). Remove chicken from marinade, letting excess drip off (but don’t wipe it dry — you want the aromatics to remain). Sear thighs 3–4 minutes per side until a deep golden-brown crust forms. The high heat promotes Maillard reactions for flavor.

Finish in the oven (if thicker) or continue on the grill: If using an oven, transfer the seared thighs to a sheet tray and roast at 425°F (220°C) 8–12 minutes until internal temperature reaches 165°F (74°C). If cooking entirely on the grill, move to indirect heat and close the lid for 6–10 minutes. Let the chicken rest 5 minutes before slicing — resting lets juices redistribute and prevents dryness.

Taste and adjust vegetables: When veg finish roasting, toss them with a squeeze of lemon, a drizzle of olive oil if they seem dry, and the remaining chopped parsley (reserve a little for garnish). Taste for seasoning — roasting concentrates flavors so a final brightening squeeze of lemon balances richness.

Assemble and serve: Spoon warm quinoa onto plates, top with a portion of roasted vegetables, and place 1–2 chicken thighs (depending on size) on top or to the side. Garnish with the remaining parsley and a lemon wedge. Serve immediately so the chicken stays juicy and quinoa warm.

Optional finishing flourish: Drizzle any resting juices from the chicken pan over the chicken and vegetables for extra savory depth; a tiny pat of butter (5–10 g) melted into the rest juices makes a rich pan sauce.