Banana bread is gluten free if made with flours such as oat, coconut and almond flour. Wheat flour is not gluten free.
When purchasing oats to make oat flour remember that oats are naturally gluten free, but may be processed in a plant that also contains glutenous products. Make sure you are getting gluten-free oats if you have Celiac disease, as this indicates the oats were processed in a facility without gluten. If you are looking for an oat-flour based banana bread, check out this recipe for PB&J Banana Bread!