Preparation

In a 3-quart saucepan combine potatoes with cold water to cover by 2 inches and bring to a boil. Add salt and simmer, covered, until potatoes are just tender, 10 to 15 minutes. In a colander drain potatoes and cool. (Potatoes may be boiled 2 days ahead and chilled, covered.)

Prepare grill.

In a skillet cook bacon over moderate heat until crisp. Transfer bacon to paper towels to drain and reserve 1 tablespoon drippings. Break bacon into large bits.

Halve potatoes and toss gently with 1 tablespoon oil to coat well. Arrange potatoes, cut sides down, on an oiled rack set 5 to 6 inches over glowing coals and grill until golden, 4 to 5 minutes. (Alternatively, potatoes may be grilled in a hot well-seasoned large ridged grill pan over moderately high heat.)

Cut scallions crosswise into 1 1/2-inch pieces and quarter pieces lengthwise.

In a large bowl toss potatoes with reserved drippings, bacon, remaining 3 tablespoons oil, vinegar, scallions, pepper, and salt to taste. Serve potato salad at room temperature.