To make the cauliflower couscous, cut the cauliflower into florets and place them in a food processor. Blend for approximately 10 seconds until the cauliflower has broken down into a fine "couscous" consistency. The pieces should be very fine and approximately 1/4 the size of a piece of cauliflower rice. Measure out 3 cups of the "couscous" and place it in a large salad bowl.
Combine the chopped tomatoes, cucumber, bell pepper, red onion, olives and optional feta in the bowl with the couscous and toss until everything is well mixed.
In a small bowl whisk together the olive oil, red wine vinegar, oregano, salt, pepper and garlic. Pour the dressing over the salad and toss until well combined. Serve or refrigerate for up to 4 days.