In a large serving bowl, whisk together the olive oil, red wine vinegar, lemon juice, honey, Dijon mustard, chopped shallot, fresh herbs, salt, and pepper until smooth.
Toss the chicken tenders with basil pesto and balsamic vinegar until evenly coated.
Heat a grill, grill pan, or skillet over medium-high heat. Cook the chicken for 8–10 minutes, turning occasionally, until fully cooked. Let it rest for a few minutes before chopping into bite-sized pieces.
Bring a large pot of generously salted water to a boil. Cook the orzo until al dente according to the package directions. Drain well.
Immediately add the warm orzo to the bowl with the dressing and toss thoroughly so the pasta absorbs the flavorful dressing.
Add the chopped chicken, feta cheese, cherry tomatoes, cucumbers, Kalamata olives, roasted peppers, and pepperoncini.
Toss gently until everything is evenly coated. This Greek Chicken Orzo Salad can be served immediately while slightly warm or refrigerated until chilled for even deeper flavor.