In a medium-sized jar with a tight-fitting lid, mix together the minced herbs and garlic, mustard, and vinegar. Add the olive oil a few tablespoons at a time, shaking well to emulsify after each addition. Season with salt and pepper.
Chill for a couple of hours before preparing the salad.
For the Salad:
Coarsely chop the tomatoes, cucumber, onion, and bell pepper. Combine in a large bowl.
Add the olives to the vegetables.
Pour three-quarters of the chilled dressing over the ingredients and toss lightly.
If needed, cut the feta cheese in large pieces. Lay the cheese on top and drizzle on the remaining dressing.
Cover with a clean dishtowel, and let stand for 20-30 minutes at room temperature to allow the flavors to blend. Serve!