Preheat grill to medium heat.
Wash and cut asparagus spears to equal sizes.
Wrap four asparagus spears with prosciutto. Repeat until all asparagus and prosciutto are used, about six bundles. Place in cast-iron skillet or disposable aluminum pan. Cover bundles with garlic powder, onion powder, pepper and butter.
Place skillet or pan on grill. Grill 15 minutes, turning bundles halfway through cooking.