Preheat the oven to 400°F. Place the chicken in a baking dish, brush with 2 tablespoons olive oil and sprinkle with 1/4 teaspoon of the salt and pepper. Cook for about 15 to 20 minutes or until done. Remove from the oven and let cool.
Meanwhile, place the bread cubes on a baking sheet and drizzle with 2 tablespoons olive oil. Sprinkle with the herbs and toss until well combined.
Bake the croutons for 10 to 12 minutes, tossing them every few minutes so they brown on all sides but do not burn. When golden brown, remove from the oven and reserve.
In a large bowl, combine the remaining ¼ cup olive oil, vinegar, garlic, mustard, remaining ¾ teaspoon of salt, and pepper. Whisk well.
Add the tomatoes, cucumber, pepper, onion, and basil, capers if using, and croutons to the bowl. Toss well to combine.
When the chicken is cool enough to handle, cut into cubes and add to the salad to serve.