Preheat your oven to 400°F (200°C).
In a large bowl, whisk together the oats, orange juice, and orange zest. Let it sit for 5 minutes to soften the oats.
In a separate bowl, whisk together the oil and eggs until well combined.
In a third bowl, whisk together the flour, sugar, baking powder, salt, and baking soda.
Add the wet ingredients (oat mixture and oil-egg mixture) to the dry ingredients and mix gently until just combined. Don't overmix!
Gently fold in the blueberries.
Divide the batter evenly among 24 paper-lined muffin cups, filling them about two-thirds full.
In a small bowl, combine the topping ingredients (chopped nuts, sugar, and cinnamon). Sprinkle the topping over the muffin batter.
Bake the muffins for 15-18 minutes, or until lightly golden brown and a toothpick inserted into the center comes out clean.
Let the muffins cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.
Enjoy your delicious homemade blueberry orange muffins!