In a mixing bowl, whisk together olive oil, lemon juice, minced garlic, dried oregano, salt, and pepper until well combined. Place chicken in the marinade, coat thoroughly, cover, and refrigerate for 30 minutes to 2 hours.

While the chicken marinates, rinse quinoa under cold water using a fine mesh strainer. In a saucepan, combine quinoa with broth, a splash of olive oil, and a pinch of salt. Bring to a boil, then reduce heat, cover, and simmer for 15 minutes. Remove from heat and let sit covered for 5 minutes.

Preheat grill over medium-high heat. Remove chicken from marinade and grill for about 6-7 minutes on each side until cooked through and internal temperature reaches 165°F. Let rest for 5 minutes before slicing.

Assemble the bowls by placing a serving of quinoa at the bottom, topping with sliced chicken, tomatoes, cucumber, red onion, olives, and feta.

Drizzle extra olive oil and lemon juice over the bowls and garnish with parsley before serving.