Whisk all barbecue sauce ingredients together. Pour the sauce into a casserole dish (9 x 13 is fine, as is 9 x 9) and add the vegetables and tempeh. Coat the vegetables and tempeh well, and allow them to marinate in the fridge for two hours (or overnight).
Divide the vegetables and tempeh evenly onto the skewers, alternating ingredients. Reserve some extra sauce for serving.
Heat the grill to medium-high. Place skewers on the grill and cook, basting occasionally, for 7 to 10 minutes, or until the vegetables are tender and everything is browning. You can also do this on a grill pan, and cook for 8 to 10 minutes on medium-high heat. Serve immediately.
Gena Hamshaw is a certified nutritionist, recipe developer, and food blogger. She shares her latest culinary adventures at The Full Helping. She's the author of two cookbooks, Food52 Vegan (2015) and Choosing Raw (2014). She enjoys yoga, sweet potatoes, cashews, and things that are smothered in sauce.