In a bowl, whisk together olive oil, vinegar, honey, salt, pepper, and basil. Set aside till ready to serve.
For Salad:
Heat a grill to high heat. Coat peach halves and onions olive oil and season with salt and pepper.
Place peaches and onions on the grill. Turn occasionally for 3-4 minutes. Peaches and onion will be tender and slightly charred. Remove peaches and onion from the grill. Allow to cool a few minutes and slice into large pieces.
Divide the lettuce between two bowls. Top with sliced grilled peaches and onion. Add blueberries, avocado, and feta. Top with honey basil dressing. Serve.