1 Preheat oven to 400°F. Cut acorn squash in half (cutting through the stem end) and scrape out seeds.2 Cut into 3/4-inch thick slices and place in a large bowl. Toss with the olive oil and half the vinegar; spread in a single layer on a large baking sheet.3 Bake for 20 minutes; sprinkle with walnuts and thyme and cook for 5 minutes more or until squash is tender.4 Drizzle with remaining vinegar and season to taste with salt and pepper.