Heat a grill or grill pan over medium for 5 minutes.
Coat grill grates or grill pan with vegetable oil. *
Grill 2 ears corn, turning occasionally, until charred, about 10 minutes. When cool enough to handle, cut kernels from cobs.
In a small bowl, whisk together ¼ cup lime juice, 2 tablespoons oil, 2 teaspoons agave, 1½ teaspoons cumin, and 1½ teaspoons coriander for vinaigrette. Season with salt and pepper to taste.
In a large bowl, combine corn kernels, 1 can rinsed and drained beans, and 4 sliced scallions. Set aside.
In a separate large bowl, add 6 cups chopped romaine and toss with half of bean and corn mixture as well as half of dressing.
Top with remaining corn and bean mixture as well as sliced avocado. Serve remaining vinaigrette on side.