In a small stainless steel bowl, whisk together the balsamic vinegar, honey, salt, and pepper until the salt has dissolved.
Gradually incorporate the extra-virgin olive oil in a steady stream while whisking vigorously to create a stable emulsion.
Toast the pecan halves in a dry pan over medium heat for 3 to 5 minutes until fragrant, then set aside to cool.
In a large chilled mixing bowl, combine the mixed spring greens and sliced red onions.
Drizzle half of the vinaigrette over the greens and toss lightly with tongs until leaves are evenly coated.
Distribute the dressed greens across four plates; top each with peach wedges and toasted pecans.
Finish each salad by sprinkling crumbled goat cheese over the top and drizzling with the remaining vinaigrette.