PREHEAT barbecue to medium-high. Pat steak dry with paper towels. Combine 2 tbsp oil with 1/4 tsp salt in a small bowl and brush over both sides of steak. Season with fresh pepper. Oil grill. Barbecue steak, lid open, until medium-rare, 4 to 6 min per side. Transfer to a cutting board and rest, covered with foil, at least 5 min.
WHISK remaining 1/4 cup oil with vinegar, jalapeno, Dijon, garlic and remaining 1/4 tsp salt in a large bowl. Season with fresh pepper. Stir in tomatoes, onion, radishes, snow peas and basil until combined.
SLICE the steak thinly against the grain and serve with the snow pea salad.