In Morrowind I went dungeon diving a lot, and I love doing it in Oblivion as well. But I remember in Morrowind so many times I would explore and dungeon dive, I would go into one that was somehow associated with either a main quest, or a misc. quest and pick up a quest item. I wouldn't know it, and it would make me totally ruin the story. That's why I sometimes pass up dungeons. Anyone else feel the same way? I just don't like to do a quest, until I am actually given the quest.

I never played Morrowind but I've never run into quest people in dungeons other than umbra.

No, because that does not happen in Oblivion. In Oblivion no important quest-giving NPCs can be killed.

This. There isn't really any way to break the main quest by exploring like you could in Morrowind or Fallout :sadvaultboy: (I skipped half of the main Fallout quest by just looking around.)

There's an item in Miscarcand that can disrupt the MQ, but it's REALLY obvious that it's something different. As long as you don't touch it until told to, you'll be fine. And after fighting any vampires near Skingrad, set the dust aside.

Otherwise, quest items generally can't be sold, so if you happen to find one by accident, it'll just remain in your inventory until it's needed.

As said above, it is hard to break a quest by dungeon diving. Either the areas within the dungeon are not accessible or sometimes there is a key-required door with no key or important people are marked essential. The game is pretty good at letting you just explore and not screw up quests. Also, the majority of dungeons have nothing to do with quests.

Now all that said, when my char is considering going into a dungeon, she usually asks my opinion. I look it up. If it is a quest related dungeon, I suggest she pass it by for now. Often she listens to me (not always though, lol).

So, supposed one accidentally picked up that really obvious thing in Miscarcand, it would just stay there until it was time to give it up?

Assuming you were able to pick it up, I think that it wouldn't let you drop or sell it,since it's a quest-related object

Picking that up prematurely can lead to a bug.

That and one dungeon for the Fighters Guild questline are the only two I could think of where you can mess up a questline.

In this game quests and questlines are protected from breaking by essential NPCs, places that need a key to enter, or something similar.

So from a quest perspective it's pretty safe to dungeon dive in TES IV: Oblivion.

First time through I ended up in many quest related areas, and often picked up quest items that were just lying around.
Its a pain and as people kindly put here it can in a few cases cause bugs, so really the best thing I can suggest is just save before picking anything up thats loose on the ground first.
Or not pick it up in the first place.

Oh, cool! Thank you guys! Now I don't have to sit there and pass up dungeons! =D I was always thinking to myself, "Meh, I want to go in here, but it might be quest related." That's great!

I think the fighter's guild line related dungeon is Swampy Cave. Stay out of that one until you're asked to go there. Entering it early prevents a spawn you need. Don't think that bug was ever fixed officially but I'm sure the Unofficial Patch fixes it. And takes care of the Miscarcand thing.

Mara

Also, stay out of any interiors in the temple of the moth priests area unless doing a related quest.

Also to note, the bug isn't game ending, it just makes a later quest more physically challenging to complete. Also, in Morrowind you could break the quest by accidentaly picking up and losing an important, unique item. Oblivion fixes this in another way in that there are very few unique artifacts to find, making most dungeons very similar to each other and, IMO, not as much fun to explore. In oblivion your just going to find leveled loot, normal items, you'll rarely find a unique named or unique appearance item, with the exception of randomly enchanted generics.