My all time favorite marinade (for veggies) is olive oil and fish sauce. I know...sounds kinda weird, but I kid you not, give it a try. The fish sauce penetrates the veggies and as they cook, the fishy taste disappears and they practically melt in your mouth. Grilled Zucchini and red onion are my favorites.
Can anyone give up some suggestions for steak/chicken/veggie marianades??