If you are following a gluten-free lifestyle, or just want to try making a pie crust out of something besides traditional wheat flour, then you can substitute with oat flour. Wheat flour and oat flour weigh the same per cup. Both weigh 120 grams. Therefore when using oat flour in lieu of wheat flour, you can simply swap one for the other in terms of the recipe. However, one thing to watch out for is that some bakers say oat flour is a little more absorbent than wheat flour. Therefore a touch more of your wet ingredients may be in order.
Read the pie crust recipe. A pie crust recipe might call for a flour, butter, water, salt and shortening. Simply substitute the amount of wheat flour with oat flour.
Measure out the flour in terms of weight. Remember that 1 cup of oat flour should weigh 120 grams. If you are making just a base pie crust, it will probably call for 1 cup. If you are making a top to the pie crust, it might ask for 2 cups or 240 grams.
Mix the oat flour and salt ingredients together in a bowl. Slowly stir in the butter and shortening using an electric mixture.
Add water 1 tbsp. at a time mixing at a low speed until the pie crust takes on a smooth consistency. This is where you might need to add an extra tbsp. or 2 of water depending on how much the oat flour is absorbing the water and moisture from the butter and shortening. The mixture should be crumbly in nature.
Wrap the mixture in plastic wrap and allow it to rest for about 20 minutes.
Roll out the pie crust. If you are placing a little extra flour on the rolling board make sure it is oat flour so that it stays truly gluten-free. Roll out the crust until it is smooth. Then form the oat flour pie crust into your pie tin. It is now ready for the filling. Bake according to the recipe directions.