Preheat the oven to 325°. Put the beets in a large roasting pan. Drizzle with the oil and sprinkle with pepper.
Cover with a sheet of parchment paper and then with a double thickness of foil, sealing tightly. Bake for 1 to 1 1/2 hours, or until the beets are tender when pierced. Remove from the oven and let cool, covered.
Meanwhile, in a medium stainless steel saucepan, combine the vinegar, sugar, ginger, cloves, bay leaf and salt. Simmer over low heat until syrupy, about 20 minutes.
Strain the syrup and let cool to room temperature.
Peel the beets. Thickly slice them or cut into 1/2 -inch wedges.
Transfer the beets to a large bowl and pour the syrup on top.
Cover and refrigerate overnight. Serve chilled or warm, in the syrup.