Whisk first 5 ingredients in bowl to blend. (Can be made 1 day ahead. Chill. Bring to room temperature and rewhisk before using.)
Cut off peel and white pith from oranges. Cut oranges into 1/4- to 1/2-inch-thick rounds. Cut each round into quarters. Transfer orange pieces to large bowl. Add remaining ingredients and toss to combine. Toss salad with enough dressing to coat and serve.