Although many beardies naturally seem to eat more greens as they age its not a good idea to just assume he will do this. The problem is, if he doesn't start eating greens on his own you now have to convince a yearling to eat greens, which is harder to do than convince a hatchling.
Try wiggling the greens around, bumping them across the bottom of the cage so they "move" like crickets. Try ripping legs off crickets and throwing them in the dish with the greens, hopefully the beardie will get some of the greens when he goes to grab the crickets. Also, try colorful things, as beardies seem to be attacted to bright veggies, finely grated carrots are relished, as are rose petals (no pesticides!)
Beardies are oppurtunistic feeders, try feeding greens before you feed the crickets, and feed them when they are the most hungry to increase the chances that they will take the greens.
Most bearides, as long as they are introduced to them at a young age, will continue to increase the porpotion of greens they eat over time. Don't be worried if you have to hand feed the greens to your hatchlings for a while, they will get the hang of it soon enough, just be persistant!!

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1.1 Common Boa-Un-Named, Ursula
1.0 Ball Python-Anabell (go figure!)
1.0 Red Tegu-Uteg
1.0 Albino Cal King-Pig
0.1 Mexican Black King-Morticia
1.1 Bearded Dragons-Unnamed, Hanabil
1.0 Albino San Diego Gopher-Unnamed
0.1 Hermans tort-Esio
1.1 JCP-Milton, Medusa
1.1 Reverse Okeetee Corn-Unnamed
0.1 Snow Corn-Unnamed
1.0 Hypo Okeetee Corn-Unnamed
0.1 Motley Okeetee-Unnamed
1.0 Western Hoggie-Wyrm
0.0.1 Rose Hair Taruntla-Unnamed
2.0 Leopard Geckos-Reptar, Pogo
4.1 cats-Tucker,Poe,Abhib,Emerald, Felicity
0.1 Bullmastiff-Asha