In a food processor, combine peaches, half of the pecans, the orange juice, vinegar, mustard and salt. Cover and process until smooth. With food processor running, slowly add oil in a thin, steady stream (vinaigrette will thicken as oil is added). Serve immediately or cover and store in the refrigerator for up to 2 days. Stir vinaigrette before serving.
In a large bowl, toss greens with 1/2 cup of the vinaigrette. Sprinkle with the remaining toasted nuts. Serve remaining vinaigrette on the side.