First, prep the vegetable. Wash and remove the stem from the mushrooms. Keep these for later. The caps you can leave alone, but cut the bigger ones in half.
Deseed and slice the bell pepper into pieces that fit the skewer. Peel and cut the onion into 8 sections to get long "petals"
Slice the squash and zucchini into thin medallions. Place all vegetables on a sheet tray to keep organized.
If using, cook and cut your veggie burger into smaller pieces.
Mix all the ingredients for the marinade. Cut the mushroom stems into small pieces and add them as well. Taste to adjust to your liking.
Preheat oven to 400°F
Skewer your vegetables in any fashion you like. Line a sheet tray with aluminum foil and place the skewers on top. Do not overlap the vegetables.
Pour the marinade on top.
Place in oven and heat for 25 minutes. You know it is done when the vegetables are soft and release a lot of juices. Serve hot!