Season the chicken breast with salt, pepper, and a pinch of dried oregano.
Grill the chicken over medium-high heat for 6-7 minutes per side until the internal temperature reaches 165°F.
Place the egg in a small pot of water, bring to a boil, then cover and remove from heat for 10 minutes before peeling and slicing.
In a small bowl, whisk together the olive oil, lemon juice, salt, and pepper to create the dressing.
Combine the mixed greens, halved cherry tomatoes, sliced cucumbers, and rinsed chickpeas in a large salad bowl.
Slice the grilled chicken into strips.
Top the salad with the sliced chicken and hard-boiled egg, then drizzle with the lemon vinaigrette just before serving.