In a large bowl, combine the whole wheat flour, rolled oats, ground flaxseed (if using), baking powder, salt, and sugar. Whisk together until well mixed.
Prepare Wet Ingredients:
In a separate bowl, whisk together the milk, egg, melted butter or oil, and vanilla extract until well combined.
Combine Ingredients:
Pour the wet ingredients into the dry ingredients. Stir gently until just combined. Be careful not to overmix; the batter should be slightly lumpy. If you’re adding any optional ingredients like berries, bananas, or nuts, fold them in gently.
Preheat Griddle or Skillet:
Preheat a nonstick griddle or large skillet over medium heat. Lightly grease with a small amount of butter or oil if necessary.
Cook Pancakes:
For each pancake, pour about 1/4 cup of batter onto the griddle or skillet. Cook until bubbles form on the surface of the pancake and the edges start to look set, about 2-3 minutes.
Flip the pancake and cook until the other side is golden brown, about 2 minutes more.
Repeat with the remaining batter, adjusting the heat as needed to prevent burning.
Serve:
Serve the pancakes warm with your favorite toppings such as maple syrup, fresh fruit, yogurt, or nut butter.