Set your oven to preheat at 350°F (177°C) and prepare two baking sheets by lining them with parchment paper.
In a mixing bowl, mash the bananas until mostly smooth but still slightly chunky. Blend in the peanut butter and vanilla extract if you like, mixing until evenly combined.
Add the oats and chocolate chips if using, stirring all ingredients until the mixture is fully combined.
Cover your cookie dough and let it rest for 20 to 30 minutes while the oven heats up.
Scoop about two tablespoons of dough per cookie onto the lined sheets; gently flatten the tops if you prefer thinner cookies and sprinkle extra chocolate chips if desired.
Bake the cookies for 10 to 12 minutes, until the edges hold firm and display a light golden color.
Allow the cookies to cool for at least 15 minutes on the baking sheet before moving them to a rack to finish cooling to room temperature.
Enjoy your wholesome and delicious oatmeal cookies as a snack or dessert.