Increase the amount of weight you can squat or leg press in GOOD FORM for 15 full-range, continuous reps by a tremendous amount, then do breathing reps until you get at least 25, preferably over 30.
If you move that total from 225 for 30 to 315 for 30, all things being equal, your legs will grow. Likewise, if you're leg pressing 600 for 30 and move that up to 800 for 30, there's no question you'll have much bigger wheels.
But you won't be able to accomplish that training legs three times a week. At best, once every five days, or twice a week with one hard session and a much easier one with top warm-up weights for much fewer reps. If that isn't enough to satisfy your OCD, follow through with just a couple sets of extensions and other jerk-off exercises (if that). You'd actually be better off doing some pull-throughs and maybe one high-rep set of a knee-friendly hack squat to failure ... assuming such a thing exists, of course
