Preheat a gas or charcoal grill on medium high heat.
Lightly brush the corn and halloumi with olive oil.
Grill the corn until lightly charred all over, about 5-7 minutes. Grill the halloumi 2-3 minutes per side until the cheese has grill marks.
When they are cool enough to handle, slice the corn off the cobs and cut the halloumi into 1/2-inch pieces.
Combine the corn, halloumi, peaches, tomatoes, chives and basil in a large bowl.
To make the vinaigrette, whisk the pesto, mustard, salt, pepper, white wine vinegar and olive oil in a small bowl.
Drizzle the vinaigrette into the salad. Toss to combine.
Notes
You can keep leftovers in an airtight container in the fridge up to 3 days. Before serving the salad, let it sit at room temperature for at least 15 minutes, so it isn’t as cold.