Place potatoes in a large pot and cover with cold water. Season with salt and bring to a boil. Reduce to a gentle simmer and cook until potatoes are just fork tender but not falling apart, about 10 minutes. Drain and let cool slightly.
Halve potatoes lengthwise and transfer to a baking sheet with green onions. Gently toss with olive oil and season with salt and pepper.
Preheat grill to medium-high heat. Grill potatoes and green onions over direct heat, turning, until crispy and lightly charred, about 3 minutes for green onions and 5 minutes for potatoes. Transfer green onions to cutting board and roughly chop, then place in a large bowl. When potatoes are ready, transfer to the same large bowl.
Add Garlic Parmesan and Herbs Snack Spread and gently stir, letting butter melt and coat potatoes. Stir in vinegar and parsley. Taste and add more salt or pepper as needed. Serve warm.