Whisk buttermilk, sour cream, herbs, lemon juice and garlic in a small bowl to combine; season buttermilk dressing with salt and pepper.
Heat a cast-iron skillet on the grill or stovetop. Working in batches, cook bacon in skillet, turning occasionally, until browned and crisp, 8–10 minutes. If cooking bacon on the grill, transfer to grate with tongs and grill bacon, turning once, until charred around the edges, about 1 minute. Transfer bacon to paper towels to drain.
Toss bread in same skillet until coated in bacon drippings. Cook, turning often, until crusty and browned, about 2 minutes.
Drizzle buttermilk dressing over iceberg wedges and crumble bacon over. Top with grilled croutons and Gorgonzola crumbles.