Cook the Quinoa: In a medium saucepan, combine 1 ½ cups of uncooked quinoa with 2 cups of water and a pinch of kosher salt. Bring it to a boil over medium-high heat, then reduce the heat to low. Cover and simmer for about 12-15 minutes until the quinoa is tender and the water is absorbed. Fluff with a fork and set aside.
Prepare the Marinade: In a jar, combine ¼ cup of olive or avocado oil, the juice of 2 lemons, 1 tbsp of honey, ½ tbsp of lemon zest, the minced 1 garlic clove, 2 tsp of dried oregano, 1 tsp of dried basil, and season with kosher salt and pepper. Shake well to combine.
Marinate the Chicken: Place the 4 boneless, skinless chicken breasts in a shallow dish and pour 1/3 of the marinade over them. Allow it to marinate for at least 15 minutes (or up to 2 hours in the refrigerator for deeper flavor).
Grill the Chicken: Preheat your grill or grill pan over medium-high heat. Remove the chicken from the marinade and discard any leftover marinade. Grill the chicken for 6-8 minutes per side until fully cooked and it registers 165°F on a meat thermometer.
Prepare the Vegetables: While the chicken is grilling, dice the 1 English cucumber, chop the 4 Roma tomatoes, and dice the 1 medium red onion. Set aside.
Assemble the Bowls: Once the chicken is cooked, let it rest for a minute before slicing it. In serving bowls, layer the cooked quinoa, sliced grilled chicken, diced vegetables, 1 cup of crumbled feta cheese, and 1 cup of kalamata olives. Drizzle with the remaining marinade.