Preheat an outdoor grill for medium heat and lightly oil the grate.

Place potatoes in a large bowl; add 2 tablespoons olive oil and toss to coat.

Cook on the preheated grill until tender, about 30 minutes. Cool, 10 to 15 minutes, cut into quarters, then place in a large bowl.

Whisk 1/2 cup olive oil, vinegar, salt, black pepper, garlic, and sugar together in a bowl until smooth; pour over potatoes. Add bacon, green onions, and parsley; toss until evenly coated.