For the pancake mix: Put the oats in the bowl of a food processor and pulse a few times until chopped. Add the flour, sugar, baking powder, baking soda, salt and lemon zest and pulse a few more times to combine. Add the oil and lemon juice and pulse to moisten the dry ingredients. Store in a resealable plastic container in the refrigerator for up to 2 weeks.
For the pancakes: Whisk together the pancake mix, milk and egg in a medium bowl until combined.
Heat a large nonstick skillet over medium heat. Lightly coat the skillet with a bit of butter or cooking spray. Drop 1/4 cup batter per pancake into the skillet; you will be able to make about 3 pancakes at a time. Cook until the edges are set and the tops are bubbly, about 2 minutes. Flip and cook until the bottoms are browned, another 1 to 2 minutes. Repeat with the remaining batter. Serve warm with your favorite toppings.