Line an 8 inch by 4 inch baking loaf pan with parchment paper, leaving some overhang for easy removal later.

Add quick oats, peanut butter and maple syrup to a large mixing bowl. Mix with a spatula until everything is evenly combined. Your mixture should be thick, like cookie dough. You should be able to shape the mixture with your hands without it sticking to your hands. If your mixture is too wet or sticky, you can add a little more oats. If it's too dry, you can add a little more peanut butter or maple syrup.

Divide the oat mixture in half. Add one half of it to your prepared baking pan and use your hands to spread and press it evenly across the bottom of your pan. The mixture will be thin, but you should have enough to cover the entire bottom surface.

Add blueberries to a small high powered blender. Blend until the blueberries become a thick liquid. It's okay if there are specks of blueberry skin, but there should not be any blueberry pieces left. Taste the puree and if you don't think it is sweet enough, you can add a little maple syrup. Carefully pour the blueberry puree over the oat mixture. It should be thick enough that it sits on top. Use a spatula to spread it evenly across the surface of the oats. It's important to wait until right before you are about to use the puree to make it. The puree thickens a lot when it sits out and will be difficult to spread if you make it ahead of time.

Place the remaining half of the oat mixture on a sheet of parchment paper. Measure the interior dimensions of your baking pan. Even if you are using an 8 x 4 inch pan, it may measure a little less than 8 x 4 inches inside. Use your hands to shape, press and spread your mixture into a thin rectangle on the parchment paper, with the same dimensions of the inside of your baking pan. This will be the oat crust placed on top of your blueberry puree. Use a thin cookie spatula to loosen and lift the oat mixture off of the parchment paper. You may be able to lift it in one piece but it's also okay if the oat crust breaks as you start to remove it from the parchment paper (you can press it back together once it's in the pan). Gently place the oat mixture crust on top of the blueberry puree. If you oat mixture broke into a few pieces, you can gently press together any cracks or breaks once it is on top of the blueberry puree. Just don't press too hard because that will squeeze up the blueberry puree.

Place bars into the fridge to set, about 2-3 hours. This will help firm up the bars. Once bars are set, cut them with a large sharp knife. Wipe your blade between each cut. Serve bars immediately. You do want to eat the bars soon after they come out of the fridge because they will get a little too soft to handle if left out at room temperature too long. Store uneaten bars in an airtight container in the fridge or freezer.