In a large bowl, whisk together orange juice, vinegar, oil, mustard, cumin, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Add salad mix, olives, red onion, and bell pepper. Mix gently to coat. Add more salt and pepper to taste.
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.