Season the chicken breast with half of the sea salt, black pepper, and dried oregano.
Grill the chicken over medium-high heat for 5-7 minutes per side until fully cooked, then let it rest before dicing into bite-sized pieces.
Rinse and drain the chickpeas and cannellini beans thoroughly under cold water.
Dice the cucumber, halve the cherry tomatoes, and finely mince the red onion and fresh parsley.
In a large mixing bowl, whisk together the extra virgin olive oil, lemon juice, and the remaining salt, pepper, and oregano.
Add the diced chicken, beans, cucumber, tomatoes, and onion to the bowl and toss well to coat in the vinaigrette.
Gently fold in the crumbled feta cheese and fresh parsley before serving.