Step 1: Cook the Quinoa. Rinse 1 cup of quinoa thoroughly under cold water. Combine with 2 cups of water or vegetable broth in a small saucepan. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes, or until all liquid is absorbed and quinoa is fluffy. Remove from heat and let sit, covered, for 5 minutes, then fluff with a fork. Spread onto a baking sheet to cool completely.
Step 2: Prepare the Chicken. While the quinoa cooks, pat 1.5 lbs (approx. 680g) boneless, skinless chicken breasts dry. Season generously with salt, black pepper, and 1 teaspoon of dried oregano. Heat a grill or grill pan to medium-high heat. Lightly brush the chicken with olive oil. Grill for 4-6 minutes per side, or until cooked through and internal temperature reaches 165°F (74°C). Remove from heat, let rest for 5 minutes, then dice into bite-sized pieces.
Step 3: Chop the Vegetables. While the chicken cools and quinoa chills, chop 1 large cucumber (or 2 Persian cucumbers), 1 pint (approx. 2 cups) cherry tomatoes (halved), 1 red bell pepper, and 1/2 a small red onion. Finely chop 1/2 cup fresh parsley. Pit and halve 1/2 cup Kalamata olives. Crumble 4 oz (approx. 113g) feta cheese.
Step 4: Whisk the Dressing. In a small bowl, whisk together 1/4 cup extra virgin olive oil, the juice of 1 large lemon (about 3-4 tablespoons), 1 teaspoon dried oregano, 1/2 teaspoon salt, and 1/4 teaspoon black pepper until emulsified. Taste and adjust seasonings as needed.
Step 5: Assemble the Salad. In a large mixing bowl, combine the cooled quinoa, diced chicken, chopped cucumber, cherry tomatoes, red bell pepper, red onion, Kalamata olives, and fresh parsley. Pour the dressing over the ingredients and toss gently until everything is evenly coated. Gently fold in the crumbled feta cheese. Serve immediately, or refrigerate for flavors to meld.