Recovery from overtraining is difficult. It is much better to pace yourself from the beginning of the season. If you cannot stay off the bike, an easy spin would be good. Perhaps try running a few days - you'll use different muscles (hamstrings) and no doubt have gorgeous legs by the end of the summer.

Another option would be to substitute weight training & give your lungs a rest. Use light weights & higher reps (15) for your legs, normal weights & reps (8-12) for upper body.