Most but not all console messages appear in one of the /var/log files -- syslog, messages, dmesg.
For the missing ones you need to enable boot logging. OEL being based on RHEL, it should be easy but the mechanism may be broken. More here
If boot logging does not work for you ...
If the system boots to a graphical login, change the default runlevel so it doesn't ...
Disable the first psuedo-terminal (the one accessed by Alt+F1) to leave it as the console device. With a bit of luck, Shift+PgUp will scroll back to the message.
If that doesn't work Ctrl+S during booting may stop console output (Ctrl+Q to resume scrolling). If that doesn't work, try a camera.