Preheat your oven to 400°F (200°C). In a small bowl, mix the olive oil, garlic powder, paprika, salt, and pepper. Brush this mixture over the chicken breasts.
Place the seasoned chicken breasts on a baking tray lined with parchment paper. Bake for 20-25 minutes, or until the chicken is cooked through and no longer pink. Allow it to rest for 5 minutes before slicing.
While the chicken is baking, rinse 1 cup of quinoa under cold water. In a pot, combine the quinoa with 2 cups of water (or chicken broth for extra flavor) and bring to a boil. Reduce the heat to low, cover, and simmer for about 15 minutes or until all the water is absorbed. Fluff with a fork.
In a large bowl, combine the cherry tomatoes, cucumber, bell pepper, and spinach. Add the cooked quinoa to the bowl and toss gently.
Divide the quinoa and vegetable mixture evenly into four meal prep containers. Slice the baked chicken and place it on top of the quinoa mix. If desired, sprinkle feta cheese over each serving.
Drizzle balsamic vinegar over the chicken and quinoa in each container. Seal the containers with lids.
Keep the meal prep containers in the refrigerator for up to 4 days.