Microwave or boil the baby lime beans slightly less than package directions. You want these to have some body. For frozen beans just defrost them in the microwave and they'll be fine. Boiling them for 1-2 mins and draining is the other option if using frozen Lima beans. They should have some bite to them and not be mushy.
Whisk together the lemon juice, oil, oregano, garlic, salt.
Mix the beans and tomatoes with the dressing and chill for at least 1 hour, preferably overnight.
Before serving toss in the feta cheese and parsley.
Adjust seasoning with more salt and pepper to taste.