IN a resealable plastic bag, combine the pork and ¼ cup of the vinaigrette and turn the meat to coat. Seal the bag and marinate in the refrigerator, turning occasionally, for 2 hours.
MEANWHILE, place squash in a medium bowl. In a small bowl, stir together the oil, rosemary, garlic, salt, and ¼ teaspoon of the black pepper. Toss to combine.
PREHEAT oven to 425°F. Line a rimmed baking sheet with foil then lightly coat with cooking spray. Remove the pork from the marinade; discard the marinade. Place the pork on one half the prepared pan. Season the pork with the remaining ¼ teaspoon black pepper. Place the squash on the other half of the pan in a single layer. Bake for 15 minutes; stir the squash; bake 10 minutes more or until squash is browned and crispy and pork is done (145°F). Remove from oven; let stand 3 minutes. Cut into ¾-inch-thick slices.
MEANWHILE, in a large bowl combine endive, frisée, apples, and pecans; drizzle with remaining ¼ cup vinaigrette and toss to coat. Divide meat and salad among four plates. Top salad with squash.
Tip: To toast pecans, preheat oven to 350°F. Spread nuts in a shallow baking pan. Bake 5 to 10 minutes or until nuts are lightly toasted.