1. Preheat oven to 425 degrees F. Microwave pierced potatoes on HIGH for 12 minutes; bake for 15 minutes. Slice off potato tops. Scoop out pulp, keeping skins intact. Mash pulp in medium bowl.
2. Heat a small skillet over medium heat; add butter. Add onion, broccoli, and salad dressing to potato pulp; mix well.
3. Brush outside of potato skin shells with oil.
4. Spoon potato mixture into shells, dividing evenly. Place on a baking sheet. Bake potatoes until heated through, about 15 minutes. Sprinkle with parsley; salt and pepper to taste.