Prepare a grill for medium-high heat.
Brush the lettuce, scallions, tomatoes and corn with olive oil.
Place the romaine lettuce, cut side down onto the grill and let cook for 4 minutes. Remove once the lettuce is slightly charred and transfer to a serving platter.
Grill scallions and tomatoes in a grill basket, turning occasionally, until charred in spots and tomatoes begin to split, 6–8 minutes. Transfer to a cutting board and slice scallions into small pieces. Grill the corn until just lightly golden. Remove from grill and cut off the cob.
Add the scallions, tomatoes, corn, cut avocado and mint to the grilled romaine platter. Drizzle with the vinaigrette and sprinkle with the goat cheese and sea salt. Serve as needed.