How about supplementation? (Vitamins, minerals, calcium carbonate)
All the insects I know of have an unfavorable calcium/phosphorus (spell?) ratio, so they should be dusted with / shaken in a vita-mineral blend suitable for reptiles occasionally and in calcium carbonate on every feeding. (I agree on the meal worm part, they should only be used as snacks - the chitin in their exoskeleton can also be hard to digest.) A diverse diet is a good start; Gryllus bimaculatus, Gryllus assimilis or other crickets, Blaptica dubia, Panchlora sp., Stilpnochlora couloniana or other hopper locusts represent a stable basic diet.
You can supplement with different larvae like the larvae of Galleria mellonella and Pachnoda marginata peregrina, Zophobas atratus - both the larvae and the beetle... Insects from Mother Nature will also be a good supplement - just make sure you don't collect from areas near busy roads or places where there is a risc that the area has been sprayed with insecticides or other agricultural sprays. I collect carabid beetles (like Carabus nemoralis, C. violaceus and C. coriaceus) in the forest and the beardies love them - they can be easily housed in a plastic tank with some untreated garden mould / sphagnum as substrate and pieces of tree bark as hideouts. The beetles feed on naked snails / slugs, earth worms and such...
(Writing all this from a Danish point of view where all these insects are available - I don't know what you can find other places.)
If it's a baby you might as well get him/her started on the greens as well, if it's an adult he/she should already be consuming leafy greens.
And how about the setup? Are the temperatures correct? UV lighting, size of the viv [...] ?
The temperature gradient should go from 40-45 deg. Celsius (aah bugger, you people use the Fahrenheit scale *taking out the ol' dusty calculator*) 104 F - 113 F directly under the basking spot (85 - 95 in the warm end of the enclosure) to approx. 78 F in the cool end.
In my humble opinion anything smaller than 120 x 60 x 60 cm or roughly 47 x 23,5 x 23,5 inches (length x depth x height) for one grown up beardie is pure maltreatment.