I am building a new steel building that will have a 1 bedroom living quarters. I will live in the building as we are building our new home over the next several years. Had the power company come out and install a 320 amp service and I split that off into two 200 amp disconnects (actually 200 main breaker panels mounted on the outside of the steel building that each have 8 circuits with pass-through lugs). I ran the wire from one of the 200 amp panels to a 32 circuit breaker box (with main breaker) just outside the living quarters (inside the building).

In the steel building I will have a 20x30 shop area. Rather than run a bunch of 12/2, 12/3, and 10/3 wire from the main breaker box near the living quarters, I thought it would be better to install a 125 amp sub-panel in the shop. That way I can just run 1/0 aluminum between the main and sub panel (actually I guess technically speaking they are both sub-panels). I do understand that I must run a 4 wire circuit (cannot connect neutral and ground on the same bus).

My question is, the main breaker panel near the living quarters does not have pass-through lugs. Can I just insert the 1/0 wires going to the shop sub-panel into the feed lugs with the 4/0 wires powering the main panel?

Thanks,
Jeff

Question should have read "125 amp", not 25 amp.

You will need to feed the sub panel from a breaker. If you "tap" onto the lugs, that circuit would be unprotected between the lugs and the panel. What would protect that length of wire?