Heat coals or gas grill for direct heat. Reserve 2 tablespoons of the chiles for Chile Vinaigrette; reserve remaining chiles for salad. Make Chile Vinaigrette.
Place potatoes in grill basket (grill “wok”). Drizzle with oil; sprinkle with salt. Shake basket to mix and turn potatoes.
Cover and grill potatoes 4 to 6 inches from medium heat 25 to 30 minutes, shaking basket or stirring potatoes occasionally, until tender. Add bell pepper to basket for last 5 minutes of grilling.
Place Chile Vinaigrette in large bowl; stir in tomatoes and remaining green chiles. Add potatoes and bell pepper to tomato mixture in bowl; toss to mix.