If cooking foil packs in the oven, preheat your oven to 425°F.
Cut 1½ pounds steak into evenly-sized 2-inch pieces. Dice 1 pound potatoes, 1 red pepper, and 1 small onion into evenly-sized 1-inch pieces.
Add the potatoes to a boiling pot of water on the stove and parboil for 5 minutes. Alternatively, add them to a heatproof bowl in the microwave covered with water and cook for 2 minutes to partially cook them.
Mix 3 Tablespoons olive oil, 2 cloves garlic, 1 teaspoon paprika, 1 teaspoon thyme, ½ teaspoon salt, ½ teaspoon pepper, and 2 teaspoons lemon juice in a small bowl.
Toss the steak, potatoes, onions, and peppers in the oil mixture.
Cut foil squares large enough to contain and fold over the steak and potatoes mixture. Divide the steak and potatoes evenly between the foil packs.
Seal up the foil packs and cook them on the grill for 10 minutes, or in a preheated oven at 425°F for around 20 minutes.
When done cooking, open the steak foil packs and finish the steak by placing it on the grill or under the oven broiler for a couple of minutes to sear.
Serve steak foil packets in the foil, or on a plate. Enjoy!