In a large serving bowl, whisk together the olive oil, red grape vinegar, lemon juice, honey, Dijon mustard, chopped shallot, fresh herbs, salt, and pepper until well combined.
Toss the chicken tenders with the basil pesto and balsamic-style vinegar until evenly coated.
Heat a grill, grill pan, or large skillet over medium-high heat. Cook the chicken for 8–10 minutes, turning occasionally, until fully cooked and golden. Let it rest for a few minutes before chopping into bite-sized pieces.
Bring a large pot of salted water to a boil. Cook the orzo according to the package directions until al dente.
Drain the orzo well and immediately add the hot pasta to the bowl with the dressing. Toss thoroughly so the warm orzo absorbs the flavorful dressing.
Add the chopped grilled chicken, feta cheese, cherry tomatoes, cucumbers, Kalamata olives, roasted bell peppers, and pepperoncini.
Toss everything gently until evenly coated. Taste and adjust the seasoning if needed.
Serve your Greek Chicken Orzo Salad warm, at room temperature, or chilled. The flavors become even more delicious after resting in the refrigerator for a few hours.