In a large mixing bowl, toss together chopped mushrooms, chopped cauliflower florets, chopped green beans, and halved grape tomatoes with the olive oil, salt, pepper, onion powder, and garlic powder.
Toss the seasoned veggies into a large skillet over medium-high heat. From here, toss and cook the veggies until they become tender and all begin to turn golden brown. Make sure any thick cauliflower florets are broken down into pieces that are tender and golden with the rest of the veggies.
Stir the remaining ingredients into the skillet. Continue cooking on a medium-high heat until the soy sauce turns the veggies an allover golden color and caramelize slightly. Serve hot right away!