Heat a grill pan over high heat. In a small bowl combine 1/2 cup oil, the garlic, a pinch of salt, and pepper. Brush vegetables with garlic oil. Place, cut side down, on grill and season with salt and pepper. Cook until well marked and slightly charred, 4 to 8 minutes per side.
Meanwhile, whisk together remaining 1/4 cup oil, the vinegar, and sugar to make a dressing. Transfer grilled vegetables to a platter and drizzle with dressing. Sprinkle with salt and pepper. Serve immediately.