Place squash in a large bowl and pour in creamy salad dressing. Cover and refrigerate for 30 minutes.
Remove squash from refrigerator and sprinkle in the parmesan cheese; mix to coat well. Stir in the flour, coating well.
Heat oil in a large skillet over medium-high heat. Carefully place squash in oil and fry until lightly browned. Turn once, and add onions. Fry until squash is browned on both sides. Using a slotted spoon remove squash and onions, and place on paper towels to drain.