In a mixing bowl, combine the olive oil, dried oregano, garlic powder, sea salt, and freshly cracked pepper. Add the chicken breasts and marinate for at least 30 minutes or overnight.
In a medium saucepan, bring the chicken broth (or water) to a boil. Stir in the rinsed quinoa, reduce heat to low, cover, and simmer for about 15 minutes until liquid is absorbed. Fluff with a fork and set aside to cool.
Preheat grill or skillet over medium-high heat. Cook marinated chicken for 6-7 minutes on each side until fully cooked (internal temperature of 165°F). Remove from heat and let rest for 5 minutes before slicing.
In a large bowl, combine diced cucumber, halved cherry tomatoes, red onion, crumbled feta, and halved kalamata olives. Squeeze lemon juice over and mix gently.
Divide cooled quinoa among meal prep containers. Top with sliced chicken and cucumber-tomato salad. Garnish with chopped parsley.
Allow meal prep bowls to cool completely before sealing. Store in the refrigerator for up to 4 days.
Notes
For an appealing presentation, consider layering the salad atop the quinoa and chicken or serve it in separate small cups.