Melt butter in a small saucepan over medium – high heat.
Add onion and garlic and cook until soft.
Stir in lemon juice, lemon zest, Worcestershire sauce, mustard, thyme, salt and pepper.
If sauce is prepared ahead of time, refrigerate and reheat when ready to use.
Preheat the grill to medium heat. If using wooden skewers, soak them in water for 15 minutes to prevent them from burning too quickly on the grill.
Cut chicken or fish into one-inch-thick cubes.
If using other vegetables, such as red onion or bell pepper, cut into one-inch squares. Cherry tomatoes work great and can go on the skewers whole. Cutting fruits such as pineapple in one-inch squares also works well.
Thread chicken or fish and vegetables evenly onto the skewers. You may choose to do separate vegetable skewers from the chicken or fish since the vegetables tend to cook quicker. Or watch the heat on your grill carefully, and alternate chicken or fish with the vegetables for more attractive skewers.
Brush skewers on both sides with Buttery Lemon-Pepper Basting Sauce and place on the grill over medium heat. Cook for about 5 to 6 minutes, brush with basting sauce again, turn and cook for another 5 to 6 minutes until the chicken or fish is cooked through.
Place chicken skewers on a clean plate and brush with basting sauce again. Serve hot.