Heat Muscat, white wine, and 6 rosemary sprigs in a saucepan over medium-low heat until warm.
Meanwhile, cut away peel and pith from oranges, keeping the segments intact, or, if desired, cut between membranes with a paring knife to release segments. Divide whole oranges or segments among 4 serving bowls. Pour wine mixture over top. Garnish with rosemary, and serve immediately.