Preheat oven to 350 degrees F (175 degrees C). Grease muffin cups or line with paper muffin liners.
Mix flour, rolled oats, baking powder, baking soda, salt, and nutmeg together in a large bowl. Combine vegetable oil, orange juice concentrate, water, egg, and vanilla extract in a separate bowl.
Stir oil mixture into flour mixture; mix until batter is smooth. Fold in blueberries; stir until combined. Spoon batter into prepared muffin cups.
Bake in the preheated oven until golden and cooked through, about 17 minutes. Cool in the pans for about 1 minute before removing.
