Where can I find Qbasic lessons?
If your main interest in Quickbasic is so that you can work on the OHRRPGCE, you should learn FreeBasic instead. The OHRRPGCE is being converted over to it. There are several links to FreeBasic tutorials are available at http://freebasic.net/index.php/support
If you just have a general interest in QuickBasic, you can go to Google (QB Tutorials category), but be warned that QuickBasic is a very old language with a lot of limitations.
If you already know how to program in some other language (C++, Python, PHP, Java, Perl, whatever) You should probably just download the source code and look at it. A programmer with any experience in other languages should be able to look at well-written QuickBasic code and understand a little of what it is doing... unfortunately most of the OHRRPGCE's existing source code is not well-written, but nevertheless, the best way to learn to swim is by getting your feet wet (In this case, getting your feet really really muddy)