Make the dressing: In a small bowl or jar, whisk together olive oil, lemon juice, red wine vinegar, garlic, oregano, Dijon, salt, and pepper. Taste and adjust acidity or salt.
It should be bright, lemony, and well-seasoned.
Prep the chicken: If you haven’t already, shred or chop cooked chicken into bite-sized pieces. Lightly season with a pinch of salt and pepper to refresh the flavor.
Chop the vegetables: Halve the tomatoes, dice the cucumber, and slice the red onion thin. Roughly chop parsley and mint.
Build the salad base: Add greens to a large bowl.
If using grains, scatter them over the greens.
Add the mix-ins: Top with chicken, tomatoes, cucumber, red onion, olives, and herbs. Sprinkle with feta.
Dress and toss: Drizzle about two-thirds of the dressing over the salad. Gently toss until everything is lightly coated.
Add more dressing as needed, keeping the texture fresh, not soggy.
Finish and serve: Taste and adjust seasoning with more lemon, salt, or pepper. Add any optional toppings like toasted pine nuts or avocado. Serve immediately, or chill for 10 minutes to let flavors mingle.