Halve potatoes and soak in cold water 15 minutes. Preheat oven to 375°.
Drain potatoes and dry with a kitchen towel. Put in a large bowl with 3 tbsp. olive oil, 2 tsp. salt, and 1 tbsp. chopped thyme and mix to coat. Spread potatoes in a single layer on an oiled rimmed baking sheet, flat side down, and roast 25 minutes. Drizzle with remaining 1 tbsp. olive oil and roast 30 more minutes, or until golden underneath.
Loosen from pan with a spatula and transfer to a serving platter. Sprinkle with parsley, lemon zest, remaining 2 tsp. thyme, and salt and pepper to taste.
Note: Nutritional analysis is per serving.