Preheat oven to 350 degrees F (175 degrees C).

In a large mixing bowl, cream together the granulated sugar and shortening until light and fluffy.

Mix in the mashed overripe bananas and large egg, scraping down the sides of the bowl, and mix well.

Mix in the pure vanilla extract.

In a separate large mixing bowl, combine the rolled oats, all-purpose flour, baking soda, ground cinnamon, salt, and ground nutmeg.

Mix the dry ingredients until thoroughly combined.

Add the wet ingredients to the dry ingredients.

Mix just until combined; it will be a wet cookie dough.

Stir in the milk chocolate chips.

Using two spoons or an ice cream scoop, portion overflowing tablespoonfuls of dough onto 2 ungreased cookie sheets, placing 12 cookies per sheet.

Bake just until golden brown, for 20 to 25 minutes.

After 10 minutes, turn and swap the cookie sheets on each rack for even cooking.

Cool the cookies on a wire rack.