I have a Geforce 6200 128mb, P4 3.0 and 1gb of RAM. (I'm upgrading soon) I'm looking for any performance enhancing mods that will allow me to play mostly above 30fps (even in wilderness!). I would prefer that these mods be compatible with Operation Optimization, though that is not 100% required. Anyone who helps me with this gets many thumbs ups from me.

I've read that Operation Optimization is obsolete and that http://tesnexus.com/downloads/file.php?id=10400 is a better option.
http://tesnexus.com/downloads/file.php?id=23208 works well for me also.
kuertee's http://tesnexus.com/downloads/file.php?id=24606 can improve performance by keeping saves clean and preventing save game bloat.
Also, you might consider kuertee's http://tesnexus.com/downloads/file.php?id=22136, which features purge-cell buffering (like Streamline) which optimize memory usage. It's not entirely compatible with streamline though, and if you use the purge cell buffer feature (the part that enhances performance), it will be completely incompatible.

For the wilderness, some good ones are http://tesnexus.com/downloads/file.php?id=5434, http://tesnexus.com/downloads/file.php?id=15278, and http://tesnexus.com/downloads/file.php?id=2069.

As a side note, with your specs it depends a lot on what graphics settings you are using (Medium, High, etc) and how many other mods you're running. You shouldn't have too many mods running with that rig, they can bog down performance significantly. Mods that add extra scripts running in the background (most mods that add extra features and behaviors to NPCs) place a big strain on your CPU, and thus have a sneakily huge effect on overall performance, even though they do not enhance graphics in any way.

I have an older computer as well. The things I have found that help are the OSR & Streamline mentioned above. I also found some reliable links for optimization over at http://tescosi.com/wiki/Oblivion/Stabilization_and_Optimization. Especially the Basic Plugin Cleaning link.

Turning off grass and disabling music help out a good bit as well. You could also turn off the refraction shader thing that affects Oblivion gates & invisibility for another boost.

I run on all low except textures, I can't stand low textures. Also I have no other mods running besides performance boosters.

By the way, my computer keeps on crashing oblivion when I have the OO mod and no wind and low poly grass mods on together. I think this is because they're incompatible, can you confirm this?

Is short grass compatible with low poly grass?