These skewers can be prepared on the outdoor grill or under broiler. If cooking on the grill, preheat to medium-high.
Heat the broiler to high. Place the peppers on a baking sheet and char them all over, about 15 minutes. Leave the door cracked a bit so steam can escape.
While peppers roast and blacken, bring a couple of inches of water to boil in a skillet. Add sausages and par-cook them by boiling them for 5 minutes.
While the sausages cook, bring a medium-size pot of water to a boil. Add onions and cook 5 minutes. Drain them then wipe off the skins and trim off ends with paring knife.
Cut each sausage into 3 pieces. On each of the four metal skewers, thread six pieces of sausage and six onions. Drizzle skewers with EVOO and season with salt and pepper, and reserve.
Place the roasted peppers in a bowl and cover tightly with plastic wrap. If you're preparing the kabobs under broiler, leave it on but drop the rack a few inches. If you are grilling outside, switch broiler off.
Cool peppers 10 minutes so you can handle them. Peel and seed them then chop them into two-inch squares or slice into 2-inch wide strips. Dress with a liberal drizzle of EVOO, salt and pepper, and sprinkle onions and hot pepper rings on top.
In a six-inch skillet over low heat or on the side of the outside grill, melt the butter, stir in garlic and parsley, and reserve.
Grill or broil the skewers for 5-6 minutes, turning every couple of minutes. Baste with the vinegar in the last minute of cooking time.
Char bread on the grill the last two minutes of cooking time and dip it in the garlic-parsley butter.
On a serving platter, arrange the balsamic-brushed cooked sausage and onions on bed of dressed peppers and surround with chunks of garlic toast. Remove metal skewers and serve.