Heat grill to medium. Once it is hot, clean the grill grate with a wire brush.
Toss the potatoes with 1 tablespoon of the oil and ¼ teaspoon each salt and pepper in the center of a 16-inch square of heavy-duty foil. Fold the foil over and seal the edges to form a packet. Grill the packet, turning occasionally, until the potatoes are tender, 23 to 25 minutes.
Meanwhile, brush the steaks with olive oil and season with ½ teaspoon each salt and pepper. Grill until an instant-read thermometer inserted into the thickest part registers 130° F, 3 to 5 minutes per side for medium-rare. Let rest for 10 minutes before thinly slicing against the grain.
Toss the snap peas, almonds, mint, parsley, lemon juice, ¼ teaspoon each salt and pepper, and the remaining 3 tablespoons of oil in a bowl. Spoon over the steak and potatoes.