Preheat the oven to 350 degrees. Place the pecans on a baking sheet and toast in the oven until golden and fragrant, 6 minutes; roughly chop.
Preheat a grill to medium-high heat on one side and medium heat on the other. Lightly brush the peaches with oil and grill over medium until nicely marked, about 4 minutes per side. Meanwhile, place a flat cast-iron skillet on the grill over medium-high heat. Add the bacon and cook until crisp; transfer to a paper-towel-lined plate.
Combine the spinach, red onion, grilled peaches, pecans and bacon in a large bowl.
Make the dressing: Mash the blue cheese with a fork in a bowl. Mix in the buttermilk, sour cream, sugar, and salt and pepper to taste. Toss with the salad just before serving.
Photography by Miki Duisterhof
Recipe courtesy the Neelys for Food Network Magazine