I have looked around on the forum maybe im blind and didnt see it. At what age/size do oscars become mature.

It's in the breeding section. Anyway, oscars become sexually mature at approximately 15 or 16 months. I've not known them to become mature at a younger age but some literature suggests a year. I think you would have to experiment with quite a few pairs to confirm this. I've done it with three and it has always been around 15 or 16 months. As for how big they are at this stage, anywhere between eight and 11 inches. The bigger the tank, the bigger the Oscar will probably be

I guess i'm blind LOL.. thank you

in my experience, oscar become mature 10 months after i got them
but i do not know how long they have been in the local fish store.
in that ten months, they had grown to 12 inches long (from original
size of 1.5 inches as juvenile)

but my latest oscar that i have now matured at 14 months under my
care. considering the time they stay at lfs, i assumed them to be
16 months old.

symptoms of maturing oscar: lip locking; moving substrate; establish
territorial area; cleaning slate or bottom glass if no slate available.
two days before spawning, they will never take any foods.

since my first oscars were rescued at about 5 inches in length i dont know what there actual age is, but they started spawning when they reached about 10-11 inches in length. by comparing them to oscar i have that i do know the age of i would guess that they were about 15 months old when it happened.