If using wooden skewers, soak them in water for at least 30 minutes before cooking. Preheat the grill to medium-low heat, around 325 degrees F.
Shuck the corn and cut into 1 1/2 rounds. Cut the zucchini into 1-inch rounds. Cut the bell pepper and onions into 1 1/2 inch square pieces, and discard pepper seeds. Trim the brussels sprouts. Work the vegetables onto the skewers in a random pattern.
Melt the butter and whisk with the Old El Paso Fajita Seasoning Mix and lemon juice.
If using metal skewers: grill for 15 minutes, dry. Then brush with the fajita butter and grill another 5 minutes. Rotate the skewers every 3-5 minutes. Brush the remaining fajita butter over the skewers once off the grill.
If using wooden skewers: Grill the skewers dry for 20 minutes, rotating them every 3-5 minutes. Then remove the skewers from the heat and brush thoroughly with fajita butter. Serve warm!