Hey mate. Super excited to see some other people so close to me. Not super well versed on the trails out Toowoomba way, since I mostly frequent the Scenic Rim area and Lamington etc. I do know that Cunninghams Gap is up your way, but I have never hiked that trail myself. There is also the Bicentennial Trail which is around that area.
According to the Lockyer Valley website these are also some other National Parks which might be out that way: Glen Rock Regional Park, Gormans Gap and Mount Campbell, Flagstone Environmental Park, White Mountain State Forest and Helidon Hills. Never been there to any, but worth doing some more research. Let me know if you find anything good mate, partner and I have a week off coming up and it would be good to find some stuff. I've been wanting to head out to Gatton to see the wild brumby herd which is apparently in one of the National Parks there.
Pic related, hidden trail in Lamington Park. Yet to go there but its supposed to be awesome.