Preheat oven to 350 °F. Line muffin tins with papers.
In large bowl, mash bananas. Add oil and egg; mix well. Add water, 2 cups baking mix, oats, and sugar. Stir until combined, then beat for 20 strokes.
Fill muffin tins 2/3 full.
Make topping: Combine 1/3 c. baking mix and brown sugar. Work with fingers to combine and remove lumps. Work in margarine to form even crumb mixture. Top muffins with crumb mixture.
Bake 20 minutes or until tests done.
Remove to rack and cool completely.
Notes
This can be made in mini loaf pans also. I use one that has 6 mini "Bundt" type loaves in a tray. Bake about 30 min for these.
If you are not allergic to milk, you can use butter.
Butter and Margarine: Butter is a dairy product made from cow’s milk. Margarine typically contains milk or soy, but there are milk-free and soy-free versions available.
Egg Substitutions: There are many egg-free products and foods available to make your recipes free of eggs. Find out more about egg substitutions.
Gluten: Gluten is a protein found in specific grains (wheat, spelt, kamut, barley, rye). Other grains are naturally gluten-free but may have cross-contact with gluten-containing grains. Look for certified gluten-free products if you need to avoid gluten. Find out more about wheat and gluten substitutions.