In a medium-sized bowl, combine all the dry ingredients (oats, chia seeds, baking powder, pumpkin pie spice, and salt) and mix until fully combined.
Crack the eggs into a large bowl, break the yolks and lightly mix then add the rest of the wet ingredients (yogurt, vanilla, brown sugar, and almond milk) and mix.
Pour the dry ingredients into the wet ingredients and mix. Note, the mixture will have a lot of liquid and won't fully combine.
Line a 9x13 baking dish with parchment paper and spray with oil. Pour the mixture into the lined baking dish. Scatter most of the chocolate chips evenly over the top, reserving a handful to add after baking.
Place the pan into the preheated oven and bake until fully set, about 25 minutes.
Remove from the oven and scatter the remaining chocolate chips over the top.
Allow the bars to cool for a few minutes, then lift the parchment paper out of the baking pan and place it on a cutting board to slice. Serve bars warm with a fork (they aren't meant to be hand-held).
To Freeze:
After slicing the bars, place them so they are not touching each other on a lined cookie sheet or cutting board to freeze until solid. Once frozen, transfer to a freezer safe zip bag for long term storage.
To Reheat from Frozen:
Place 1 bar on a plate and microwave on high for 1 minute. Let stand for 30 seconds before serving.
Notes
Each bar has 5g of fiber (18% of the USDA-recommended daily value) from natural sources, and 7.5 grams of protein. If you want to bump up the fiber content even more, you can dissolve fiber powder (like Benefiber) into the almond milk before making the recipe. Pumpkin pie spice, or pumpkin spice, is a blend of other spices. You can often purchase this blend premixed in the spice section, or you can make it yourself. Combine 2 teaspoon cinnamon, ½ teaspoon nutmeg, ½ teaspoon ginger, ¼ teaspoon allspice, and ¼ teaspoon cloves (all ground).