Place oven racks in upper and lower thirds of oven and preheat oven to 350. Spray 2 large baking sheets with nonstick spray, if necessary.
Put oats in blender and process until finely ground. Combine oats, flour, baking soda and salt in small bowl. With an electric mixer on low speed, beat butter, brown sugar, egg and vanilla in large bowl until well blended. Add flour mixture and beat until blended. Stir chocolate into dough.
Drop dough by level tablespoonfuls onto baking sheets 2 inches apart. With glass dipped in flour, or with your fingers, press each mound to make 2-inch rounds. Bake until lightly browned along edges, 9-11 minutes, rotating baking sheets halfway through baking time. Let cool on baking sheets on wire racks about 1 minute. With spatula, transfer cookies to racks and cool completely