Combine orange juice concentrate, milk, water, powdered, sugar, vanilla, and ice cubes in a blender.
Blend until smooth and frothy, then divide between four cups and garnish with orange slices, if desired. Serve with a straw!
Notes
If you don't have orange juice concentrate or prefer to make your orange julius with fresh orange juice, just replace the orange juice concentrate and water called for in the recipe with 2 cups of fresh orange juice or 4 peeled oranges instead.