Endurance training( >15 Rep squats/deadlifts) and consistent diet will slim your legs up.. type 1 muscle fibers are formed from endurance training and are relatively smaller in diameter than type 2 muscle fibers which are formed through strength/power training.
2nd check your lifting mechanics. When you do a squat or deadlift where is your center of gravity? Do you feel a lot of your weight coming forward towards your toes. This is typical in alot of people who are quad dominant. Your center of gravity should be straight down through your legs, straight down through center of ankle, and out the bottom of your heel at all times. Your toes should not come off of the ground, your entire foot should be planted/stable on the ground with the emphasis of your weight through The heels. Even on the up phase you you should drive through your heels. This is the biomechanical correction that will engage your HAMSTRING and GLUTES reducing tension placed on the quads. This will distribute force through both front and back leg muscle balancing out your quads and eventually reducing their size.
The first motion of your squat is not down. You need a forward lean(head above or infront of toes), while simultaneously sticking butt out behind you (anterior pelvic tilt) and bending knees so femur rotates back and around a stable knee joint. The knee joint should remain close to the same spot during your squat as when you were standing up straight. Slight forward motion of the knee is ok, definitely keep knees behind toes, and once again center of gravity through your heels.
If you can't keep a straight back or release the hips(keep butt stuck out) during squat, you cannot do a squat properly and this puts alot of stress on the quads. This is usually do to hamstring/glute inflexibility, or deficient erector spinae muscles.
Keeping a healthy diet that supports weightloss will also reduce the size of your quads
If you lost 20 pounds your quads would decrease significantly in size. Make sure to research proper ways to diet/exercise while losing weight to maintain as much muscle mass as possible, and lose as much bodyfat as possible.