To prepare the vinaigrette, drain oranges in a colander over a large bowl, reserving 1/4 cup syrup. Discard remaining syrup.
Combine 1/4 cup syrup, oil, and next 4 ingredients (white wine vinegar through pepper) in a small bowl; stir with a whisk until blended.
To prepare the salad, place oranges, lettuce, beans, and hearts of palm in a large bowl; drizzle with vinaigrette. Toss gently to coat.