In a small saucepan, cover the lentils with water by an inch or two, bring to a boil and simmer until soft, about 15 minutes. Drain and let cool.
Preheat the oven to 400ºF and line a 12 cup muffin pan with large paper liners. In a medium bowl, soak the oats in the milk and yogurt for 30-60 minutes, until the milk is absorbed into the oats. Stir in the brown sugar, oil, eggs, lemon zest and cooled lentils.
In another medium bowl, whisk together the flours, baking powder, baking soda and salt. Gently stir the dry ingredients into the oat mixture until nearly combined. Fold in the blueberries, being careful not to over-mix.
Spoon into the muffin papers and bake until golden on top, springy to the touch and a tester comes out clean, about 20–25 minutes. Tip the muffins in the pan to allow steam to escape.