In a shallow dish or a zip-top bag, combine 2 tablespoons olive oil, 1 tablespoon balsamic vinegar, dried oregano, garlic powder, salt, and pepper. Add the chicken breasts and turn to coat completely. Let marinate for at least 15 minutes at room temperature or up to 4 hours in the fridge.

While the chicken marinates, prepare the vinaigrette. In a small bowl or a glass jar, combine the extra virgin olive oil, 3 tablespoons balsamic vinegar, honey (or maple syrup), Dijon mustard, and minced garlic. Season with salt and pepper. Whisk or shake vigorously until well combined and emulsified.

Preheat your grill or a grill pan to medium-high heat. Place the marinated chicken breasts on the grill and cook for 6-8 minutes per side, or until cooked through with an internal temperature of 165°F (74°C).

Transfer the cooked chicken to a cutting board and let it rest for 5-10 minutes to allow the juices to redistribute. After resting, slice the chicken against the grain into thin strips.

In a large salad bowl, combine the fresh baby spinach, sliced strawberries, toasted pecans, crumbled feta, and thinly sliced red onion (if using).

Arrange the warm, sliced grilled chicken over the top of the salad. Drizzle with about half of the balsamic vinaigrette and toss gently to combine. Serve immediately with the remaining dressing on the side.