Preheat the oven to 425 degrees. Cut the potatoes in half or quarters, so all potato pieces are the same size. Place on a large baking sheet (or 2 smaller baking sheets) and drizzle with 1½ Tbsp. oil, salt, and pepper.
Wash potatoes, cut in half, and place in saucepan of cold water. Cook, covered, over medium heat for 25 to 30 minutes or until tender.
Drain and dice potatoes when cool.
Add vegetables and egg to potatoes, and toss.