Margarine Substitute using powdered milk
Found this and tried it using several different types of cooking oil (olive, canola, corn, etc.) and they all worked equally well. It was actually the method of incorporating that made a bigger difference. Use a small whisk and really whisk the oil in (incorporating) as you drizzle it into the water/milk mixture.
Ingredients:
 roughly 1/2 cup powdered milk
roughly 1 1/2 cups of chosen cooking oil
2/3 cups of water
couple of drops of yellow food coloring if desired 
Mix water and food coloring with powdered milk until completely dissolved. Drizzle the cooking oil into the milk/water mixture and whisk as you drizzle. You need a nice, even incorporation of the oil.
If your mixture is still too soft for your preference, you can mix in a little additional powdered milk. You can also add just a little bit of salt if you desire.