I have a natural lean build, but for the last three years I've been working out with free weights. I've been able to get good size on my upper body but my legs are lagging big time.

I DO SQUATS, but maybe not enough sets or I'm not using enough poundage although my glutes have improved. Could you recommend a routine for me along with some nutritional supplements that might help thank you very much I just turned 40 in case thats a factor

If you are serious about leg size you need to be doing either the Strength and Power Programs or the Bodybuilding Mass programs. Both of these programs have an intense amount of leg work. They are "real" workouts to get real results. Also, you should definately consider taking creatine, glutamine, and a qualtiy meal replacement like Met-Rx or Myoplex. If you do this, you will improve!