Rinse quinoa and place in a saucepan with 2 cups water and a pinch of salt. Bring to a boil, reduce to a simmer, cover, and cook 15 minutes. Remove from heat, let stand covered 5 minutes, then fluff with a fork.

Whisk olive oil, lemon juice, minced garlic, oregano, salt, and pepper in a bowl. Add chicken, turn to coat, and let marinate while quinoa cooks, about 10 minutes.

Heat a slick of oil in a large skillet over medium-high heat. Sear chicken 5-6 minutes on the first side, flip, reduce heat to medium, and cook 6-8 minutes until internal temperature reaches 165°F. Rest on a cutting board 5 minutes, then slice.

Stir together yogurt, 1 small grated garlic clove, 1 tbsp lemon juice, dill, and a pinch of salt. Add a teaspoon of water if too thick.

Divide quinoa among bowls, top with sliced chicken, cucumber, tomatoes, red onion, olives, and feta. Drizzle with yogurt sauce and serve.