I carry a G19 at 4 o'clock position at times. I almost ALWAYS carry it OWB in one of several good leather or kydex holsters - the value of a good belt and good holster, cannot be overstated. I struggled concealing anything from the day I started carrying (right after my 18th birthday), until I got to the US and discovered REAL carry belts!
For reference, I'm right at 6' and 250lbs (could stand to lose another 15 lbs, but who's counting?). My daily clothing is jeans and t-shirt or button up plaid type shirt, that's almost as good at hiding a gun than Hawaiian shirts.
Depending on your AO, think about wearing some kind of under shirt. It makes a world of difference.