Combine whole wheat flour, oats, cornmeal, flaxseed meal, brown sugar, baking powder, and baking soda in a large bowl; stir in buttermilk and egg until just smooth.

Heat a large skillet or griddle over medium heat; coat with cooking spray. Drop batter by large spoonfuls onto the griddle; cook until bubbles form and edges are dry. Flip; cook until browned on the other side. Repeat with remaining batter.