1. Heat grill to medium. Brush the bread slices on both sides with olive oil. Grill until lightly charred on both sides, 3 to 4 minutes. Let cool slightly; cut into large cubes.
2. In a large bowl, toss bread cubes with tomatoes, cucumber, and basil. Drizzle with vinegar and ¼ cup olive oil, season with salt & pepper. Toss to combine and serve!