Prepare a medium (375°F) gas or charcoal grill fire.
In a large bowl, whisk the mayonnaise and vinegar until combined.
In another large bowl, toss the potatoes, pepper, and scallions with 2 Tbs. of the oil, 1 tsp. salt, and 1/2 tsp. pepper. Rub the chorizo all over with the remaining 1 Tbs. oil.
Grill the vegetables and chorizo, turning occasionally, until the scallions are charred in places and the potatoes and pepper are tender, 3 to 5 minutes for the scallions, 6 to 9 minutes for the peppers, and 12 to 15 minutes for the potatoes. If using cured (Spanish-style) chorizo, cook long enough to warm it through, about 8 minutes. If using uncooked (Mexican-style) chorizo, cook until it registers 145°F on an instant-read thermometer, about 15 minutes.
Transfer the scallions and pepper to a cutting board. Transfer the potatoes to the bowl with the mayonnaise mixture and toss. Coarsely chop the scallions and pepper, toss them with the potatoes, and season to taste with salt and pepper.
Cut the chorizo on the diagonal into thick slices and serve with the potato salad.
nutrition information (per serving):
65, Fat Calories
580, Saturated Fat
31, Monounsaturated Fat
39, Polyunsaturated Fat
Photo: Scott Phillips