Whisk together oil, garlic, ginger, citrus juice, and zest. Season with salt and pepper to taste.

Alternatively thread shrimp, onions, and peppadews onto metal or presoaked wooden skewers. Place kebabs in a baking dish and pour ginger mixture over top. Marinate at room temperature, turning occasionally, for 10 minutes.

Transfer kebabs to a preheated grill, turning and basting with marinade occasionally, until lightly charred and cooked through, about 4 minutes.