Hi,
I did not try Oracle Forms, but it is my understanding, that as they are shown in the browser, they must be rendered as html markup. As TestComplete supports web testing, it should support Oracle Forms in web application as well.
If Forms are shown in the browser not as html markup but using some other means (e.g. as an own-drawn ActiveX control) then TestComplete might have problems.
The best way is to request TestComplete trial at
http://smartbear.com/products/qa-tools/automated-testing-tools/ (
http://smartbear.com/products/qa-tools/automated-testing-tools/free-testcomplete-trial/) and give it a try.