During the summer growing season you can make the most of just about any fresh produce you can find—crisp radishes, sweet sugar snap peas, cherry tomatoes, or chunks of baby cucumbers will make a hearty chicken salad all the more irresistible.
Heat grill to medium-high heat. Brush chicken with 1 tablespoon oil; season with salt and pepper. Grill about 8 minutes, turning once, or until no longer pink in center. Remove from grill; cut into bite-size pieces.
Meanwhile, whisk remaining 3 tablespoons oil, balsamic, vinegar, garlic salt and freshly ground pepper in a large serving bowl. Top with spinach, berries, avocado, and onion. Gently toss ingredients together until well coated with dressing.
Add chicken to salad; toss once more and serve.
Substitute in chunks of butternut squash or cauliflower, long strips of carrot, thickly sliced zucchini, or large cubes of eggplant.