Oatmeal-date bars have long been a staple sweet in America. Their popularity has never gone out of style; rich date filling sandwiched in a crispy oatmeal crust makes these treats worth licking your fingers! If you like crunch, try adding a cup of chopped pecans or walnuts.
Position a rack in the lower third of the oven, and preheat to 350 degrees F. Grease a 9-inch square baking pan and set it aside.
Combine the oats, flour, brown sugar, baking soda, salt and zest in a medium-size bowl and stir to blend. Add the butter and mix in with your fingers, a fork or a pastry blender until the mixture is crumbly. Pat half of the mixture into the prepared pan and reserve the remainder.
Place the dates, sugar, lemon juice and water in a small pan and bring to a boil over high heat. Cook, stirring constantly, until the mixture thickens slightly, about 3 minutes. Remove the pan from the stove and let the filling cool for 10 minutes. Spread the date filling over the crust in the baking pan. Pat the remaining oat mixture over the filling.
Bake until the topping is golden brown, 25 to 30 minutes. Transfer the pan to a wire rack and let cool for at least 10 minutes before cutting into squares. Store in an airtight container for up to 3 days.