In a large bowl, whisk together olive oil, lemon juice, minced garlic, oregano, thyme, salt, and pepper. Add chicken thighs and toss to coat evenly. Marinate for at least 30 minutes, or up to overnight in the refrigerator.

Meanwhile, rinse quinoa in a fine-mesh strainer until water runs clear. In a medium saucepan, bring chicken broth to a boil. Add quinoa, reduce heat to low, cover, and simmer for 15 minutes until liquid is absorbed. Remove from heat and let stand 5 minutes, then fluff with a fork.

For the tzatziki, combine Greek yogurt, grated cucumber (squeezed dry), minced garlic, lemon juice, dill, and salt in a bowl. Mix well and refrigerate until ready to serve.

Heat a large skillet over medium-high heat. Remove chicken from marinade and cook for 6-7 minutes per side, until internal temperature reaches 165°F and chicken is golden brown. Let rest for 5 minutes, then slice.

Prepare vegetables by dicing cucumber, halving cherry tomatoes, and slicing red onion. Chop fresh parsley.

To assemble bowls, divide quinoa among 4 bowls. Top with sliced chicken, cucumber, tomatoes, and red onion. Dollop with tzatziki and garnish with fresh parsley. Serve immediately.