Prepare the Tofu: Press the tofu for at least 15-20 minutes to remove excess moisture. Cut the tofu into 1-inch cubes.
Marinate the Tofu: In a bowl, mix the tamari or soy sauce, apple cider vinegar, maple syrup, smoked paprika, garlic powder, onion powder, ground cumin, dried oregano, and freshly ground black pepper. Add the tofu cubes to the marinade and gently toss to coat. For more flavor, let the tofu marinate for at least 30 minutes or up to overnight.
Prepare the veggies: Wash and dry the bell peppers, zucchini, and red onion. Cut the red, orange, and green bell peppers into 1-inch pieces. Slice the zucchini into thick rounds. Cut the red onion into large chunks.
Marinate the Vegetables: In a large bowl, mix the balsamic vinegar, salt, and freshly ground black pepper. Add the red bell pepper, orange bell pepper, green bell pepper, zucchini, yellow squash, and red onion to the bowl. Toss the vegetables until they are evenly coated with the balsamic mixture. Allow the vegetables to marinate for at least 15-20 minutes.
Assemble the Skewers: If using wooden skewers, soak them in water for at least 30 minutes to prevent burning. Thread the marinated tofu cubes and vegetables onto skewers, alternating between different vegetables and tofu (save some marinade for later).
Grill the Skewers: Preheat the grill to medium-high heat. Place the skewers on the grill and cook for 10-15 minutes, turning occasionally, until the vegetables are tender and the tofu has grill marks*.
Serve: Remove the skewers from the grill and let them cool slightly before serving. Serve the grilled tofu skewers with your favorite dipping sauce or over a bed of rice or salad.