1. Halve squash.
2. Remove and discard seeds.
3. Quarter to fit in a large pot. Add water to 1 inch.
4. Bring to boil, cover, reduce to simmer and cook 20 to 30 minutes, or until tender.
5. Remove and cool.
6. Scrape squash pulp from rind to make 4 cups.
7. Drain on paper towels to remove excess moisture. In large bowl, combine squash with mushrooms, onions, peppers and dressing.
8. Mix and refrigerate. Serves 8.