Lightly brush the corn with olive oil and grill over medium-high heat. Turn occasionally until tender and slightly charred. Let it cool before slicing the kernels off the cob.
In a small bowl, whisk together olive oil, balsamic vinegar, honey, mustard, and salt. Whisk until smooth and well combined. Taste and adjust seasoning if needed.
In a large bowl, combine spring mix, kale, strawberries, blueberries, pistachios, avocado, and grilled corn. Drizzle with the vinaigrette and toss gently. Sprinkle goat cheese on top and finish with fresh black pepper before serving.