Preheat the grill to medium-high. Place the corn directly on the grill and cook for 3-4 minutes per side, until nicely charred. Remove and let rest until cool enough to touch.
Once cooled, cut the corn from the cob. Add it to a large salad bowl along with the quinoa, tomatoes, and jalapeño.
If using, toast the pumpkin seeds in a dry skillet or toaster oven until golden brown, about 1-2 minutes. Add the seeds to the bowl and toss to combine the salad.
Add dressing ingredients to a jar. Seal the jar and shake until combined. Pour over the salad and toss. Taste and adjust seasonings, if needed.
Serve warm or, if making ahead, chill for 1-2 hours before serving.