Lightly spoon flour into dry measuring cups, and level with a knife. Combine flour, milk, sugar, and egg in a blender; cover and process until smooth. Pour batter into bowl; cover and chill 30 minutes.
Place an 8-inch crepe pan or nonstick skillet coated with cooking spray over medium heat until hot. Remove pan from heat. Pour a scant 1/4 cup batter into pan; quickly tilt pan in all directions so batter covers pan with a thin film. Cook about 1 minute.
Carefully lift edge of crepe with a spatula to test for doneness. The crepe is ready to turn when it can be shaken loose from the pan and the underside is lightly browned. Turn crepe over; cook 10 seconds on other side.
Place crepe on towel; cool. Repeat procedure until all batter is used, stirring batter between crepes. Stack crepes between layers of wax paper or paper towels to prevent sticking.
Note: Coat pan with cooking spray only as needed while cooking the crepes. To make ahead, layer crepes between sheets of wax paper, and store in a zip-top bag in refrigerator.