01 - Whisk together olive oil, lemon juice, minced garlic, salt, and pepper in a bowl. Add chicken breasts, ensuring even coating, and marinate for at least 15 minutes at room temperature.
02 - Heat grill or grill pan over medium-high heat until properly preheated for cooking.
03 - Brush peach halves lightly with olive oil to prevent sticking and enhance caramelization.
04 - Place marinated chicken breasts on the hot grill. Cook for 5 to 7 minutes per side until internal temperature reaches 165°F and juices run clear. Remove from heat and let rest for 5 minutes before slicing.
05 - Place peach halves cut-side down on the grill. Cook for 2 to 3 minutes until distinct grill marks appear and fruit begins to soften. Remove and slice each half into wedges.
06 - Combine baby spinach, sliced red onion, fresh basil, crumbled feta cheese, and toasted nuts in a large salad bowl.
07 - Combine extra-virgin olive oil, balsamic vinegar, honey, Dijon mustard, salt, and pepper in a small jar. Shake vigorously until fully emulsified and thickened.
08 - Arrange sliced grilled chicken and warm peach wedges over the salad base. Drizzle with balsamic vinaigrette and toss gently to coat evenly. Serve immediately, garnished with additional fresh basil if desired.