Rinse and toast the quinoa. Place 2 cups dry quinoa in a fine-mesh sieve and rinse under cold water for 30–60 seconds to remove the bitter saponins on the surface — this keeps the final salad bright, not soapy. Shake away excess water. Heat a medium saucepan over medium heat with 1 teaspoon olive oil, add the quinoa and toast, stirring, for 2 minutes until it's aromatic and begins to look translucent; toasting deepens the quinoa’s nutty flavor and prevents a dull, one‑note grain.

Cook the quinoa. Add 4 cups water (2:1 water to dry quinoa) and a pinch (1/4 tsp) of salt. Bring to a vigorous simmer, reduce to low, cover and cook gently for 12–15 minutes until the grains have absorbed the water and the little germ ring is visible. Remove from heat and let rest, covered, 10 minutes so steam finishes cooking the quinoa — this step yields light, fluffy grains instead of gummy ones. Fluff with a fork and spread on a tray to cool slightly while you prepare the rest.

Make the lemon‑herb marinade. In a bowl whisk together 2 tablespoons olive oil, zest of 1 lemon, 2 tablespoons fresh lemon juice (about half a lemon), 1 tablespoon chopped parsley, 1 clove minced garlic, 3/4 tsp kosher salt and 1/4 tsp black pepper. The oil and acid in the marinade both flavor and tenderize the chicken; the short marinating time (20–30 minutes) gives brightness without starting to 'cook' the protein.

Marinate the chicken. Pat the chicken breasts dry with paper towels (dry surfaces sear better) and place them in a shallow dish or zip‑top bag. Pour the marinade over the chicken, turning to coat. Let sit at room temperature for 20–30 minutes (or up to 2 hours in the fridge). If you marinate longer than 30 minutes, refrigerate and bring back to room temp for 20 minutes before cooking so the meat cooks evenly.

Make the dressing. In a small bowl whisk together 3 tablespoons olive oil, 2 tablespoons fresh lemon juice (about 1 lemon), 2 tablespoons chopped parsley, 1 clove minced garlic, 1/2 tsp kosher salt and 1/4 tsp black pepper. Taste and adjust — the dressing should be bright and slightly oily so it coats the quinoa and veggies without weighing them down.

Preheat the grill or skillet. Heat an outdoor grill to medium‑high (400–450°F / 200–230°C) or put a heavy‑bottomed skillet (cast iron preferred) over medium‑high heat and add 1 tablespoon olive oil. A smoking‑hot cooking surface gives a quick sear that locks in juices and creates attractive grill marks; the small amount of oil prevents sticking.

Cook the chicken. Place the marinated breasts on the hot grill or skillet. Cook without moving for 3–4 minutes until a golden crust forms, then flip and cook another 3–4 minutes. Use an instant‑read thermometer: pull at 160°F (71°C) — carryover will bring it to 165°F (74°C) while resting. Searing first develops flavor through the Maillard reaction; monitoring temperature prevents a dry, overcooked breast.

Rest and slice the chicken. Transfer the cooked breasts to a cutting board and let rest 5–7 minutes, loosely tented with foil. Resting allows juices to redistribute; slicing immediately will leak them out and dry the meat. Slice the chicken thinly against the grain for the most tender bites.

Assemble the quinoa salad base. While the chicken rests, put the slightly warm (or room‑temperature) quinoa in a large mixing bowl, add the halved cherry tomatoes, diced cucumber, chopped parsley (reserved), and the lemon dressing. Toss gently — adding the dressing to warm quinoa helps it absorb flavor; tossing now ensures each grain is seasoned before it meets the greens.

Build and serve. On a platter or individual plates place 2 cups mixed greens per person as a bed. Spoon roughly 1 1/2 cups of the dressed quinoa‑vegetable mixture over the greens (the recipe makes about 6 cups cooked quinoa mixture; portion ~1.5 cups each). Top with sliced grilled chicken and finish with a light grinding of black pepper and a small drizzle of olive oil or an extra lemon wedge. Serve immediately so the greens stay crisp and the chicken remains warm.

Storage notes. Leftovers keep well separately: refrigerate quinoa salad and sliced chicken in airtight containers up to 3 days. Store dressing separately if you plan to eat the quinoa with greens later to avoid wilting the leaves.