Bring ingredients together: remove the grilled chicken from the fridge and let it sit at room temperature for 5–10 minutes while you assemble the other components. Warming the chicken slightly prevents it from seizing up and helps it reheat evenly when you briefly warm it — this keeps the texture tender.

Warm & fluff the quinoa: if your quinoa is chilled, warm it gently in a microwave for 20–30 seconds or in a small saucepan over low heat with a teaspoon of water. Fluff with a fork to separate the grains. Warming and fluffing allows the quinoa to better absorb the dressing and prevents the salad from feeling cold and clumpy.

Make the dressing: in a small bowl or jar whisk together the extra-virgin olive oil, lemon juice, Dijon mustard (if using), chopped herbs, a pinch of salt and several grinds of black pepper until emulsified. Emulsifying the oil and acid with a little mustard binds the dressing so it clings to the quinoa and greens instead of pooling on the plate.

Dress the quinoa first: place the warm, fluffed quinoa in a mixing bowl and spoon about half the dressing over it. Toss gently until the quinoa is evenly coated and has absorbed some of the vinaigrette. Dressing the quinoa first seasons the grains throughout and builds flavor from the base up.

Prepare the salad base: in a large bowl combine the mixed salad greens, halved cherry tomatoes and sliced cucumber. Season lightly with a pinch of salt — salt on the vegetables pulls out moisture and concentrates their flavor, but avoid over-salting since feta is salty too.

Reheat the chicken (optional): if you prefer the chicken warm, quickly warm the sliced grilled chicken in a hot skillet for 1–2 minutes per side with a teaspoon of olive oil, just until heated through and slightly golden. Searing briefly refreshes the crust and deepens the chicken’s flavor; don’t overcook or it will dry out.

Assemble the salad: fold the dressed quinoa into the bowl with the greens and vegetables. Arrange the sliced grilled chicken on top, then sprinkle the crumbled feta across the salad. Toss gently at the table or serve composed so the feta sits on top — both presentation styles work; composing keeps some contrasting textures intact.

Finish and serve: drizzle any remaining dressing over the plated salad, grind a final pinch of black pepper, and if you like, a tiny drizzle of extra-virgin olive oil. Serve immediately. The contrast of warm quinoa and chicken with cool greens, plus the briny feta, is what makes this dish uplifting and satisfying.