My company needs to convert many vendors "en masse" to ACH, is there a quick way to do this?

Here's the easy decision:

How many vendors to change.
Time to make each change manually.
Fully costed employee per hour time.
vs
Cost of a 3rd party software add-on.
Configuration.

Remember, you still have the same information acquisition costs unless you off-load this to your vendors directly and provide them with the ability to enter some system to record the info.

I've had to do things like this in the past but not with Oracle.

Generally, what I have found worked the easiest was to download current information from the system, frequently to Excel. Make the changes there and create a master upload file. Then reload that corrected information back to the accounting systems for each entity.

I've also been involved where we've used third party software or hired a contractor to update the data. But the results have usually ended up less than satisfactory and required extensive review with quite a bit of manual correction on top of the extraordinary costs of the software and/or consultants who did the work.

Short answer to you question is no. If you software version supports direct ach output you need to
1. Contact the bank and get the format they want ( CTX, CCD, etc.) and transmission protocol (https, sftp, FTP with pgp, etc.)
2. Setup and test bank connectivity
3. Contact several vendors to get ach transmission. My rule is always five to ten.
4. Pilot with those five to ten fora week in test then a month in prod. Determine if you will send remittance advices and if so how.
5. During pilot. Reach out to your other vendors with what your policy is and what they need to do to take part.

If done right it's a 3 month project. Minimum.

I am converting our vendor to ACH as we speak. It has been around a three month project. Most of the work has been done manually getting the information directly from the vendors and uploading it into NetSuite. I have talk to our NS rep and I understand that we can set up a portal with our vendors who can update the information via the portal but that is another project.