Get your taxes done using TurboTax

I was confused, as well, but I'll tell you how I got past it. I purchased and downloaded Turbo Tax Deluxe (after the Online TurboTax I usually fill-out said I needed to use it).  Also, I've had to use AuditDefense by TurboTax in the past, so I HIGHLY recommend adding it. Below was my process for filing in Oregon as an RDP:

FEDERAL
1. I start a new return on TurboTax Deluxe.

2. I fill out the whole thing (Status: Single, Marital Status: Registered Domestic Partner) and get near the end. I am prompted how I want to process this. Choose "e-file" ONLY for FEDERAL. You will NOT be processing your STATE return.  I'm unsure if I could have just skipped the entire STATE section, but I kept getting errors so I just powered through it.
3. Confirm only your FEDERAL was e-filed. 

4. Have your RDP do the exact same thing for their own FEDERAL return. Confirm only their FEDERAL was e-filed, as well.

FEDERAL ("Mock" or "As-If")

1. Start a new return in TurboTax Deluxe. 

2. When prompted, make sure you choose "Married" and filing "Jointly".

3. Complete your FEDERAL part by filling out/uploading every form between you and your RDP.  For example, if she has 2x W-2 and you have 1x W-2, you are putting all 3 in.
4. Get to the end, but DO NOT E-FILE!  Only print out this new FEDERAL return.  Make sure you not only print it, but save it as a .PDF so you have a backup, as well. Once printed, set it aside for later. This is your "Mock"/"As-If" copy. Its sole purpose is to be mailed with the STATE return.

STATE - OREGON
1. Once the FEDERAL returns were e-filed, decide on whether you want to file your STATE jointly or separately. There are pros and cons to both. I decided to do jointly (mainly because I was so done with this process and didn't want the extra work and papers. Don't be like me).
2. Start a new return in TurboTax Deluxe.
3. When prompted, select "Married" and either filing "Jointly" or "Separately"; whichever you decided on. For the rest of my instructions, it will assume you are filing "Jointly".
4. I don't know if there is a way to skip the FEDERAL part; the only important part is the STATE. But, go ahead and complete this tax return factoring in both of you when answering the questions.
5. Near the end, DO NOT E-FILE! Only print out the STATE return, and save it as a .PDF for a backup, as well. Set your STATE return aside.

FINAL STEPS

1. Now that you have your FEDERAL "Mock"/"As-If" return and the STATE return printed, follow ALL the instructions CAREFULLY on Page 1 of that printout. I almost accidentally mailed my returns with those instruction pages as the cover pages.  For example, I missed the part where it wanted certain copies of our W-2 forms attached.  Also, I don't believe you are allowed to staple things on the STATE return. There are some odd rules, so attach it some other way.  There are picture examples of where to attach it on the return.

2. After reading the instructions carefully, make sure you both sign the fields in your STATE return that are required. Go through the pages carefully.  I wasn't sure we needed to sign the FEDERAL Mock"/"As-If" return, but we did anyway.

3. I purchased a large envelope from UPS, put both my FEDERAL "Mock"/"As-If" and STATE return (with all their attachments) into the envelope.  I sealed it, had UPS put my name and the RDP's name on the "From" section, and mailed it to the address specified on the TurboTax return's STATE instructional page.  They had to mail it out as USPS. Make sure you have tracking, and save that tracking number.

I hope this helps. I'll be doing post-editing for minor spelling or grammar errors.