Heat oven to 375° F. Line a standard 12-cup muffin tin with paper liners. In a food processor, process the flour, oats, flaxseed meal, pecans, baking powder, baking soda, and salt until finely ground.
In a large bowl, whisk together the yogurt, sugar, butter, orange zest and juice, egg, and vanilla. Add the flour mixture and mix just until incorporated (do not overmix). Fold in the blueberries.
Divide the batter evenly among the muffin cups. Bake until a toothpick inserted in the center comes out clean, 22 to 25 minutes.*Measure the flour by spooning it into a dry measuring cup, then sweep off the excess with a knife.