Maybe I'm missing something obvious, but I can't enter outline-minor-mode
from my init.el, nor from a .el file loaded via the --load option.

Let enter-outline.el have file contents:
  (outline-minor-mode 1)

Create an empty C file:
  touch /tmp/foo.c

Start Emacs:
  emacs -Q --load enter-outline.el /tmp/foo.c

"Outl" does not appear in the minibuffer and C-c @ is an undefined key
binding.

Next:
  C-u 1 M-x outline-minor-mode

And now the minor mode is started.

---

In GNU Emacs 24.3.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.10.4)
 of 2013-06-18 on psd15
Windowing system distributor `The X.Org Foundation', version 11.0.70101000
System Description:    Red Hat Enterprise Linux Client release 5.4 (Tikanga)

Configured using:
 `configure
 --prefix=/redacted/user/boreilly/sw/emacs-install-trunk-20899d085afe62520113b5acbfe3dbba57823dc9
 --with-gif=no'

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: C/l

Minor modes in effect:
  outline-minor-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t
  abbrev-mode: t

Recent input:
C-c @ C-u 1 M-x o u t l i n e = <backspace> - m o <backspace>
i n o r - m o d e <return> M-x r e p o r t <tab> <
return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading cc-langs...done
Outline minor mode enabled

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message cl-macs gv format-spec
rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils noutline outline easy-mmode cc-langs cl
nadvice cl-lib cc-mode cc-fonts easymenu cc-guess cc-menus cc-cmds
cc-styles cc-align cc-engine cc-vars cc-defs time-date tooltip
ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd
fontset image regexp-opt fringe tabulated-list newcomment lisp-mode
register page menu-bar rfn-eshadow timer select scroll-bar mouse
jit-lock font-lock syntax facemenu font-core frame cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev
minibuffer loaddefs button faces cus-face macroexp files text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process dbusbind
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty emacs)