In a small bowl, whisk together the lemon juice, minced garlic, olive oil, oregano, salt, and black pepper to create a marinade.
Place the chicken breasts in a resealable plastic bag or shallow dish and pour the marinade over the chicken. Seal the bag or cover the dish and refrigerate for at least 30 minutes, or up to 4 hours for more flavor.
Preheat the grill to medium-high heat.
Remove the chicken from the marinade and discard the marinade. Grill the chicken for 6-7 minutes per side, or until fully cooked and the internal temperature reaches 165°F (75°C). Remove from the grill and let rest for 5 minutes before slicing.
While the chicken is resting, prepare the meal prep bowls. Divide the cooked quinoa evenly among 4 meal prep containers.
Top each portion of quinoa with grilled chicken slices, halved cherry tomatoes, diced cucumber, crumbled feta cheese, and sliced avocado.
Sprinkle chopped fresh parsley over the top of each bowl for garnish.
Allow the meal prep bowls to cool before sealing them with lids. Store in the refrigerator for up to 4 days.
Notes
For added flavor, consider marinating the chicken overnight.
You can substitute quinoa with brown rice or couscous if preferred.
Feel free to add other vegetables such as bell peppers or spinach for additional nutrition.