Place apple juice in a small saucepan, and bring to a boil over medium-high heat. Cook until reduced to about 3 tablespoons (about 10 minutes). Combine reduced apple juice, vinegar, oil, salt, and pepper, stirring with a whisk.
Combine greens, grapes, apple, and pear in a large bowl. Drizzle with apple juice mixture; toss gently to coat. Sprinkle with cheese and nuts.