I've been doing this and my legs have responded quite well to it.
leg curls 4 x 20
leg ext 4 x 20
squats 4 x 20
Do all sets to damn near failure. And for squats, use a weight that makes it tough to get 10 reps. Then the last 10 reps dig for each rep, even if you have to take like 20 deep breaths between each reps.