Preheat oven to 375. Spray a large baking dish (at least 9 by 13) with Pam ~ olive oil Pam is nice. Peel onions and slice them into rounds about 1/2 " or more thick. Separate the rings then toss them with the sage, pepper, salt and vinegar. Heap the seasoned onions in the baking dish, spray lightly with pam and cover with foil and bake for 30 min. Remove the foil, give the onions a stir, cover and return to the oven. After 15 min, stir again (they should be starting to brown all over) and return to the oven, uncovered, 20 min or more or until the juices reduce to a syrup and the onions are caramelized. Heap them in a bowl and garnish with parsley.