This salad’s earthy flavors heralds the arrival of fall. Grating garlic on an Oxo or Microplane zester/grater delivers the same burst of flavor as crushing garlic in a press, but it’s faster and easier to clean up.
1. Preheat oven to 425°F. Coat large rimmed baking sheet with cooking spray.
2. Blanch green beans in boiling, salted water 2 minutes. Drain, and rinse under cold water. Set aside.
3. Cut 6 1/2-inch-thick wheels from neck of squash. (Reserve remaining squash for another use.) Peel and halve squash wheels. Toss squash and shallots in bowl with 1 1/2 Tbs. oil; season with salt and pepper, if desired. Place squash and shallots cut side up on baking sheet. Transfer green beans to same bowl, and toss to coat with oil that remains in bowl. Place green beans and grapes on baking sheet, separated slightly from squash and shallots. Roast 8 minutes, or until green beans are crisp-tender and grapes are warmed through. Remove green beans and grapes to foil sheet. Roast squash and shallots 15 to 20 minutes more, or until browned.
4. Whisk together remaining 2 1/2 Tbs. oil, vinegar, rosemary, and garlic in bowl. Season with salt and pepper, if desired.
5. Divide watercress among serving plates. Divide squash, shallots, green beans, and grapes among serving plates, and drizzle with dressing.