You can try to offer the greens / veg early in the day and hold the live prey until later, some will begin to eat once they get a little more hungry but will resist if they already had or expect to have live prey very soon.
You can also try to offer a variety of different things, Butternut Squash seems to be a favorite among beardies, once they begin eating one or two types of veg / greens they are often more inclined to branch out.
Good Luck.