Preheat the grill to medium-high.
Chop the red pepper, zucchini, and red onion into large chunks. If the mushrooms are large, slice in half.
Place the vegetables into a plastic storage bag. Pour in sriracha and olive oil and shake the bag until evenly distributed. Let sit for 30 minutes to an hour.
Thread the vegetables onto four long, wooden skewers, alternating between different ingredients. Sprinkle with a dash of salt.
Cook 2-4 minutes per side or until the edges are lightly charred, rotating to ensure all sides are cooked. Serve immediately.
