Mash the banana in a bowl until smooth with no large chunks.
Mix in the peanut butter and yogurt until fully blended into a creamy base.
Add the rolled oats and chia seeds, stirring until combined; adjust consistency with water if too thick or crumbly.
Shape the mixture into bite-sized balls or discs appropriate for your dog's size.
Chill the treats in the refrigerator for at least 30–45 minutes to set.
Serve immediately; store leftovers in an airtight container in the fridge for up to 5 days or freeze for longer storage.