Rinse the peas under cold water.
If using frozen peas, thaw them in a bowl of warm water.
Dice the cucumber and red onion into small pieces.
Chop the fresh parsley finely.
In a large mixing bowl, combine the peas, cucumber, red onion, and parsley.
In a separate bowl, whisk together the olive oil and apple cider vinegar.
Pour the dressing over the pea mixture.
Season with salt and pepper to taste.
Toss everything together until well combined.
Let the salad sit for about 10 minutes before serving.