Combine the tomatoes, cucumbers, onion, capers, 2 tablespoons of the oil, 2 tablespoons of the vinegar, and 1/2 teaspoon each salt and pepper in a medium bowl. Let sit for 10 minutes to allow the vegetables to absorb the flavors.
Meanwhile, toss the beans with the parsley, 1 tablespoon of the oil, the remaining tablespoon of vinegar, and 1/4 teaspoon each salt and pepper.
Drizzle the toasts with the remaining 2 tablespoons of oil. Divide the tomato mixture among the toasts and top with the Feta.
Serve the toasts with the bean salad.