In a mixing bowl, add the first 6 ingredients; stir to combine.
In a jar or other container with a tight-fitting lid, add the oil, vinegar, mustard, cumin, garlic, salt and pepper to taste; secure lid and shake well to mix.
Pour dressing over vegetables; toss to coat.
Cover and chill for 4 hours.
This is good served on a bed of mixed salad greens.