Cut the pork tenderloin into 1 inch cubes. In a medium sized bowl, add the zucchini, yellow squash, red bell pepper, and red onion.
Add the olive oil and tuscan seasoning blend and toss until coated.
Thread the pork cubes on skewers along with the zucchini, yellow squash, red pepper, and onion. Grill for 8-10 minutes until the meat is done to desired liking (should reach an internal temperature of 145 F). Remove from the grill and serve.