Preheat grill to medium-high heat (350-400°). In a large bowl, toss together potatoes, onions, bell peppers, olive oil and steak seasoning. Spread potatoes out on a large piece of heavy-duty grill-safe foil, with the edges of the foil bent up into a “basket” and cover with another large piece of foil.

Place foil packet on grill and grill for 20 minutes. Remove top piece of foil; sprinkle cheese evenly over potatoes and continue to cook an additional 5 minutes (without top piece of foil). Remove from grill and top with green onions.