In a shallow, non-porous dish or bowl, mix together olive oil and melted butter. Stir in lemon juice, mustard, basil, and garlic, and season with salt and pepper. Add shrimp, and toss to coat. Cover, and refrigerate for 1 hour.
Preheat grill to high heat. Remove shrimp from marinade, and thread onto skewers. Discard marinade.
Lightly oil grill grate, and arrange skewers on preheated grill. Cook for 4 minutes, turning once, or until opaque.
Serve with a garden salad, rice pilaf, garlic toast and beverage.