Cook shallots and ginger in oil in a small heavy saucepan over medium heat, stirring occasionally, until softened and golden, about 5 minutes. Stir in vinegar and boil until reduced by about half, about 2 minutes. Add soy sauce, preserves, and 1/4 teaspoon each of salt and pepper and simmer, uncovered, stirring occasionally, 15 minutes.

Purée sauce in a blender until smooth (use caution when blending hot liquids), then cool to room temperature.Divide chicken between 2 large sealable bags and pour marinade over chicken. Seal bags, pressing out excess air, and marinate, chilled, turning bag over occasionally, at least 8 hours.

Preheat oven to 425°F with rack in middle.Line a 17- by 12-inch shallow heavy baking pan with 2 slightly overlapping sheets of foil, then lightly oil foil. Arrange chicken (with marinade) in 1 layer in pan. Roast chicken, turning once, until deep brown, cooked through, and glazed, about 40 minutes total.