Preheat gas grill to medium-high heat. Lightly coat 4 pieces of tinfoil with cooking spray. Divide the ground beef into 1/4 pound portions and form into patties.
To build dinner packs, place sliced potatoes, onions, and carrots on the foil. Place hamburger patties on top of the veggies and 1.5 teaspoons of butter on top of the patty. Sprinkle with Montreal Seasoning. Close the packets.
Place packets on the grill grates, seam side down and cook for 10 minutes. Turn and continue to cook for an additional 15 minutes. Remove and carefully open.