My daughter and I are vegetarian, just off Oasis of the seas. I have good news and bad news for you. I’ll post a full review later, but for now:
MDR has 1 vegan appetizer, entrée and dessert every night. On 2 nights there was an additional Indian main that could be made vegan. Some were excellent (Greek moussaka), some were iffy (couscous stuffed red pepper - was just a large amount of couscous). There was no source of protein in any of them. So yes, bring protein bars!
Other venues such as the Windjammer had several dishes that might have been vegetarian or vegan, but it was not always clear as nothing was labelled. We did ask, but the servers didn’t know. Some would go to the kitchen to ask for us, some didn’t offer. We discovered that you could ask for a veggie burger at the burger station, and they would cook it specifically for us. We relied on this a lot. Not sure how much protein there is in it, but it was good and filling.
We tried Playmakers for their veggie burger, but the service was appalling - no fault to our server - she was very busy, but we waited a long time to be acknowledged, then served, and never got our drinks. Johnny Rockets also has a veggie burger.
we had the best luck with the Solarium bistro - felafel, hummus and other dips, as well as veggie stir fry and other veggies. Ample bread available.
Overall it was lacking in choice and especially lacking in alternative proteins. Quality was OK. Service was in MDR was slow.
Do bring protein bars.