Stir oats, flour, brown sugar, baking soda, and baking powder together in a bowl; cut in butter using a pastry blender until mixture is mealy and butter pieces are uniformly small.
Press half of oat mixture evenly into the bottom of a 9x13-inch baking pan.
Cook dates with water in a small saucepan over medium heat until they fall apart and are easily mashed with a wooden spoon, about 10 minutes; remove from heat and stir in vanilla extract.
Spoon date mixture evenly over oat mixture in baking pan; sprinkle remaining oat mixture evenly over top and press into place.
Bake in the preheated oven until crust is golden at the edges, about 30 minutes; remove to cool completely on a wire rack. Cut into bars.
