1. Remove giblets and trim necks from quail; save for another use. Rinse birds, pat dry, and lightly sprinkle with salt and pepper.
2. In a deep 11- to 12-inch frying pan over medium-high heat, melt 2 tablespoons butter. Add as many birds as will fit in pan and brown on all sides, 12 to 15 minutes. Lift out as browned, put in a bowl, and add remaining birds and more butter, if needed, to pan. When all the birds are out of pan, discard fat.
3. To pan, add cranberries, 1 cup water, brown sugar, vinegar, cinnamon, allspice, and cloves. Stir over high heat until simmering. Return birds and accumulated juices to pan.
4. Cover and simmer over low heat, turning birds over after 10 minutes, until thighs are tender when pierced, 20 to 30 minutes total. With a slotted spoon, transfer birds to a warm platter.
5. Smoothly blend flour with 2 tablespoons water, then mix into pan. Stir over high heat until sauce comes to a rolling boil. Season with salt and pepper to taste, pour over birds, and garnish platter with watercress.