When I let my 7 month old Lab off leash to run around he eats things he finds on the ground. Any ideas for how to stop this?

First of all, I would stop letting him off leash until he's trained and understands what yuck means. I start teaching this to my puppies from day one, right now I have a 6 month old dog that is close to 100% responsive to YUCK on leash but if I let him loose I guarantee he's going to eat things he finds and swallow them. Dogs need to be trained to respond to this and then they need to generalize this to all situations. Being on a leash and obeying doesn't mean he understands it, as you can see from his behavior.

There are two options, you can train him to respond to a remote collar so that you have a way to communicate with him off-leash. Another option is to train him to wear a muzzle that prevents him from picking up things off of the ground. We have customers that do both of these things and with proper training they are both options.

For now and through the training process he should not be allowed off leash. The more he practices ignoring you and getting rewarded (eating stuff on the ground is a reward for him) the harder your job to retrain him will be.