Whisk all of your dressing ingredients into a mixing bowl and set aside.
Place the chicken into another bowl and add sea salt, pepper and garlic powder.
Drizzle oil and using your clean hands generously rub the seasoning all over the chicken.
Cover and allow to marinate in the refrigerator for at least 30 minutes, or overnight.
While the chicken is marinating; tear your spinach into bite-size pieces if desired and slice your red onion thinly.
Preheat your grill or a heavy bottomed pan (cast iron is great) over medium-high heat.
Carefully place your marinated chicken onto the preheated grill and grill until each side is nicely charred, about 8-10 minutes in total, and internal temperature reads 165 degrees f.
Set chicken aside on a board to rest, covered, then slice.
In a large serving bowl, add spinach, grilled chicken, corn, berries, pecans, and onion.
Drizzle the dressing over your salad, and toss.
Garnish with crumbled feta cheese and serve.
Enjoy!