Heat a grill or grill pan over medium-high heat. Lightly brush the ears of corn and the romaine lettuce on all sides with the grapeseed or olive oil. Set aside.
In a large bowl, combine the tomatoes, 2 tablespoons of olive oil, and minced garlic; toss to coat, then season with salt and pepper to taste. Set aside to marinate.
When the grill has heated, brush the grates with olive oil. Place the corn directly on the grill and cook for 8 minutes, turning every few minutes as it chars.
While the corn is cooking, make the dressing by combining the dressing ingredients in a blender. Process until the dressing is smooth with flecks of basil throughout, but no large chunks of ingredients remain. If the dressing is too thick, blend in additional water 1 tablespoon at a time; season with additional salt if needed.
At this point the corn should be done. Remove from the grill and set aside to cool. Add the halved romaine hearts to the grill, sliced side down, and grill for 3-4 minutes until slightly charred and beginning to wilt. Remove from the grill
To assemble the salad, lay the grilled romaine cut side up on a large serving platter, remove the kernels of corn from the cob with a knife, and sprinkle them over the romaine. Spoon the marinated tomatoes over the corn, discarding any juices that have collected in the bowl. Drizzle the salad with prepared dressing and serve.
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