Using toothpick, pierce sausages in several places.
Transfer to medium skillet; add enough water to reach depth of 1/4 inch. Bring water to boil over high heat. Reduce heat, cover skillet and simmer sausages 5 minutes.
Uncover; continue to simmer until water cooks away and sausages are brown and heated through, turning sausages occasionally, about 5 minutes. Transfer sausages to 2 plates.
Add enough oil to drippings in skillet to measure 2 tablespoons. Heat over medium-high heat.
Add potatoes (with onion) and red onion. Cover; cook until potatoes are golden brown, stirring occasionally, about 5 minutes.
Mix in parsley and vinegar. Season with salt and pepper. Spoon potato salad next to sausages.
NOTE: Look for diced potatoes with onion in the supermarket's refrigerated deli case or in the freezer section. Pair the main course with sauteed spinach, coleslaw, good mustard and dark bread. A pint of ale adds gusto; apple pie is the finishing touch.