Season the chicken breast with salt and black pepper, then grill for 5–7 minutes per side until fully cooked. Let it rest for 5 minutes before slicing.
Cook the corn if needed and allow it to cool slightly.
Dice the avocado, halve the cherry tomatoes, and thinly slice the red onion.
In a large salad bowl, combine the avocado, corn, cherry tomatoes, and red onion.
Add the sliced grilled chicken on top of the vegetables.
Whisk together the olive oil and fresh lemon juice, then drizzle the dressing over the salad.
Gently toss everything together and serve immediately. Garnish with chopped cilantro or parsley if desired.