Begin by cutting the skirt steak into 2-3 pieces, ensuring they're manageable for grilling. In a mixing bowl, combine olive oil, minced garlic, lemon juice, and salt. Coat the steak pieces thoroughly with this marinade and allow them to marinate for 15-20 minutes at room temperature.

Prepare the corn by rubbing the ears with olive oil for added moisture and flavor. Preheat your grill to medium-high heat, about 400°F (204°C). Place the corn on the grill and cook for roughly 12 minutes, turning occasionally until charred. Remove the corn and let it cool before cutting the kernels off the cob.

Increase the grill temperature to high heat. Add the marinated steak pieces to the grill, cooking for about 3 minutes on each side for medium-rare doneness. Use a meat thermometer to check for a target internal temperature of 130°F (54°C). Let the steak rest for 10 minutes before cubing.

In a small bowl, whisk together olive oil, minced garlic, lemon juice, and a pinch of salt. Taste and adjust seasoning if needed; refrigerate to blend flavors.

In a large salad bowl, start layering your ingredients: chopped romaine lettuce, cubed steak, grilled corn kernels, diced avocado, crumbled cotija cheese, marinated red onions, and sprinkle fresh chives. Drizzle the dressing, toss gently to combine, and serve.