You can make oat flour and substitute it for wheat flour. Fruit crisp, oatmeal cookies, oat pie crust work well with all wheat flour substituted with oat flour. In products like fruit cookies (pumpkin, banana, etc), muffins, quick breads, oat flour by itself is gummy or dense. For these items, it's best to use combination of flours (wheat/oat, or oat/rice/bean flour, etc.).
Rolled oats (not ground) can be used to substitute a portion of wheat flour in a recipe. Use 2 times the rolled oats as wheat flour called for.