If using frozen corn, thaw in a bowl of Luke-warm to cool water, drain and place in large mixing bowl.
Dice the cucumber by slicing into half inch rounds, then each round getting cut into 8ths, like a cross section of 1/4ths and then 8ths. Add to the mixing bowl of corn.
Dice the green onions finely, and the cilantro. Add both to the bowl and stir all ingredients together.
In a separate jar or bowl, combine the ingredients for the vinaigrette and stir vigorously.
Pour vinaigrette over the salad and mix in crumbled feta cheese. Add additional feta to the top of the salad and serve or refrigerate for up to 2 days.