It is an african cichlid from Lake Malawi which will grow to be 5-6 inches long. Although the water parameter needs of your fish do not match and forum members will tear you a new one, it should be alright for a few months until you decide if you want to invest in an african tank setup or leave it as it is. If you leave it with the oscars they will quickly outgrow it and, unless by some miracle they are mellower than Cheech & Chong, will kill it.
As far as specific species, it is probably a yellow lab (Labidochromis caeruleus) but there are several yellow species. To know for sure we need a picture of it from the side.