1 bunch baby beets (8 to 10), scrubbed and stems trimmed to 1 inch
1/3 cup white-wine vinegar
1/2 teaspoon coarse salt
1/3 cup extra-virgin olive oil
Fill a large pot with 1 to 2 inches water and bring to a boil. Place squash slices in a steamer basket, then place in pot. Cover and cook until squash is just cooked through, about 8 minutes. Remove with a slotted spoon and transfer to a 9-by-13-inch baking dish. Let cool completely in a single layer.
Preheat oven to 425 degrees. Wrap beets in parchment-lined foil and roast until easily pierced with a knife, about 50 minutes. Let cool completely. Remove skins (keep stem ends intact, if desired.) Transfer to a shallow bowl.
Whisk together vinegar and salt in a small bowl. Add oil in a slow, steady stream, whisking until emulsified. Divide vinaigrette between squash and beets and toss to coat.
Squash and beets can be made 1 day ahead and stored in refrigerator.