Preheat the grill to medium-high heat or the oven to 400°F (200°C).

In a mixing bowl, combine the ground beef, mixed vegetables, diced onion, ranch seasoning, garlic powder, salt, and pepper.

Mix until well combined.

Cut four large sheets of aluminum foil, about 12 inches long.

Divide the meat and vegetable mixture evenly among the foil sheets.

Fold the foil over the mixture and crimp the edges to seal tightly.

Place the foil packets on the grill or in the oven.

Cook for 25-30 minutes, or until the meat is cooked through and the vegetables are tender.

Carefully open the packets and serve hot.