Preheat oven to 375 degrees F. Grease and flour a muffin pan or use paper liners.
In a small bowl, combine oats and buttermilk, and let stand 5 minutes.
In a medium bowl, combine flour, baking powder, baking soda and salt; set aside.
In a large bowl, beat together the egg, applesauce, brown sugar and vanilla. Blend in the oat-buttermilk mixture. Stir in the flour mixture, just until moistened. Fold in the strawberries. Fill muffin cups 2/3 to 3/4 full. Bake in the preheated oven for 15 to 20 minutes or until toothpick inserted into the center comes out clean.