Place the tomatoes, cucumber, bell pepper, and red onion together in a large bowl.
Make the vinaigrette by whisking together the vinegar, minced garlic, minced oregano, and Dijon mustard in a small bowl.
Slowly add the olive oil to make an emulsion. Taste then season with sea salt and freshly cracked pepper, to taste.
Pour the vinaigrette over the vegetables in the bowl.
Add the feta and olives then toss lightly. Set aside to allow flavors to mingle for 30 minutes.
Toss before serving and add a bit of freshly cracked black pepper, if desired. Serve. Enjoy.