Preheat grill to medium-high.
Brush corn with 1 teaspoon oil. Grill, turning occasionally, until some kernels are slightly charred, 8 to 10 minutes. Cut the kernels from the cobs.
Meanwhile, whisk the remaining 3 tablespoons oil, vinegar, chili sauce, miso, garlic and salt in a large bowl.
Add spinach, tomatoes, scallions and the corn; toss to combine.
Serve topped with cilantro, if desired.
