Iin a large (2 qt.) baking dish, whisk 8 eggs, 1/2 cup milk and 2 tbsp. orange liqueur (such as Grand Marnier). Lay the 8 slices of bread in the egg mixture, turning often until the bread is soaked through, 2 to 3 minutes. In a griddle or large skillet, melt 1 tbsp. butter over medium heat. Add 4 soaked bread slices and cook until golden brown and cooked through, 2 to 3 minutes per side. Repeat with 1 more tbsp. butter and the remaining bread.
Segment 2 oranges. In a small bowl, toss the segments with 2 tsp. orange liqueur. Scatter the segments over the French toast; dust with confectioners’ sugar.