Boil a large pot of salted water. Add the green beans and cook until tender crisp, 1 to 2 minutes. Use a spider to remove to a bowl of ice water. Drain well, pat dry and place the beans in a large bowl. Combine with the feta cheese, tomatoes and red onions.
Toast the almonds in a small skillet, 2 to 3 minutes. Remove to a plate.
Whisk together the olive oil, red wine vinegar, basil, garlic and some salt and pepper. Pour the dressing over the green beans and sprinkle with the toasted almonds. Let marinate in the refrigerator for 1 hour before serving.