For the salad dressing: whisk together the oil, vinegar, honey and poppy seeds in a medium bowl.
Heat a skillet over medium-high heat and season the chicken on both sides. Cook the chicken until browned and cooked through, about 4 to 6 minutes per side. Once cooked, remove from heat and slice, then set it aside.
In a large bowl, toss together the mixed greens, sliced peach, sliced chicken and sliced avocado. Top with the walnuts.