Dice tomatoes and drain.

Dice watermelon.

Cube green bell pepper.

Cube cucumber.

Thinly slice radishes.

In a large bowl, combine tomatoes, watermelon, green bell pepper, cucumber, and radishes.

Toss the vegetables with 2 tablespoons of olive oil.

Add half of the feta cheese, green onions, and mint to the salad.

In a food processor, combine the remaining feta cheese, green onions, mint, and olive oil.

Add yogurt and oregano to the food processor.

Process until just blended, being careful not to over-mix.

Season the dressing with salt and pepper to taste.

Mix the dressing into the salad.

Chill for 5 minutes before serving.