Blend oil, vinegar thyme and garlic in blender until garlic is chopped; season dressing with salt and pepper
Place steak in a 13x9x2 inch glass baking dish. Pour 1/3 cup of dressing over and turn to coat. Cover and chill for 30 min. Pro tip: can be made up to 4 hours ahead - if chilling steak longer than 30 min be sure to bring back to room temp before grilling
Preheat the oven to 450. Toss shallots in 2 tablespoons of dressing and put on baking sheet. Roast shallots until caramelized and tender stirring occasionally, about 20 min. Set aside.
If grilling outside, heat up the grill now OR preheat the oven on broil. Cook steak to desired doneness, about 4 min per side for medium rare. Let steak rest 5 min, thinly slice across the grain on diagonal.
Place greens and shallots in a large shallow bowl; toss with enough dressing to coat. Place steak in the middle, sprinkle with goat cheese. Pass any remaining dressing when you serve.