Should be safe even in Phase 1. In fact, I had a great recipe that had you cut tomatoes in half, then pile pesto on the cut surface of each and broil them. The top became crispy and wonderful!!! 
I like adding balsamic vinegar, olive oil, and flavored LF feta cheese to green beans, but I bet it would work with other veggies.
I've used some of the premade marinades at my local Wegman's; our favorite is "Chicken BBQ" used on veggies that we then grill. It's SO good! Just use the same rules as for dressings: 3g of sugar or less.
Check out the FAQ. There's a thread there on how to eat more veggies when you hate them all that might be useful.
