Greek Salad

1 hothouse cucumber, unpeeled, seeded, and sliced 1/4-inch thick   1 red bell pepper, large-diced  1 yellow bell pepper, large-diced  1 pint cherry or grape tomatoes, halved  1/2 red onion, sliced in half-rounds  4 oz feta cheese, 1/2-inch diced (not crumbled)  1/2 cup castelvetrano olives, pitted For the vinaigrette:  2 cloves garlic, minced  2 teaspoon fresh oregano, chopped  1/2 teaspoon Dijon mustard  1/4 cup red wine vinegar  1 teaspoon sea salt  1/2 teaspoon freshly ground black pepper  1/2 cup good olive oil  Place the cucumber, peppers, tomatoes and red onion in a large bowl.   For the vinaigrette, whisk together the garlic, oregano, mustard, vinegar, salt and pepper in a small bowl. Still whisking, slowly add the olive oil to make an emulsion. Pour the vinaigrette over the vegetables. Add the feta and olives and toss lightly. Set aside for 30 minutes to allow the flavors to blend. Serve at room temperature. Serves 6