In a gallon sized freezer bag combine all of the ingredients for the marinade. Add in the steak cubes and toss to coat. Refrigerate for at least one hour or up to 24 hours.
Heat a gas or charcoal grill.
Toss the cubes pineapple, peppers, mushrooms, onion, zucchini, and yellow squash with the olive oil, salt, pepper, and garlic powder. Using 12 metal skewers thread a piece of zucchini, a piece of pineapple, a piece of onion, a meat cube, one type of pepper, a piece of squash, and a mushroom. Repeat this sequence two to three times, ending with the mushroom.
Grill kabobs over direct heat until the meat is browned and the veggies are beginning to char. Turn the kabobs every 2 minutes so that they cook evenly.
Transfer to a serving plate and squeeze a lemon or lime wedge over each if desired.