Preheat the oven to 400°F (200°C). Toss the butternut squash cubes with a little olive oil, salt, and pepper, and roast for 15-20 minutes until tender.
In a small bowl, whisk together the apple cider vinegar, Dijon mustard, maple syrup, olive oil, salt, and pepper to make the vinaigrette.
In a large bowl, combine the mixed greens, apple slices, roasted butternut squash, dried cranberries, pecans, and feta cheese.
Drizzle with the vinaigrette and toss gently to coat. Serve immediately.