Step 1: In a small bowl, whisk together the olive oil, lemon juice, minced garlic, oregano, and parsley to create the marinade.
Step 2: Place the chicken breasts in a shallow dish or resealable bag and pour half of the marinade over them. Let marinate in the refrigerator for at least 30 minutes.
Step 3: Preheat your grill to medium-high heat. Lightly oil the grates to prevent sticking.
Step 4: Place the chicken breasts and the corn cobs on the grill. Grill the chicken for 6-7 minutes per side or until the internal temperature reaches 165°F (74°C).
Step 5: Grill the corn for about 8-10 minutes, turning occasionally, until lightly charred on all sides. Remove everything from the grill and let the chicken rest for 5 minutes.
Step 6: Carefully cut the corn kernels off the cob and place them in a large mixing bowl. Add the diced avocado, halved tomatoes, and red onion.
Step 7: Toss the salad with the remaining marinade and season with salt and pepper. Slice the chicken and serve it alongside or on top of the salad.