1. Heat a grill to medium (350° to 450°). Toss potatoes with 1 1/2 tbsp. oil in a medium bowl. Grill, turning as needed, until browned and tender when pierced, about 20 minutes.
2. Return potatoes to same bowl and sprinkle with lemon zest, chives, salt, and remaining 1 1/2 tbsp. oil, then toss to coat evenly.