I purchased an Osprey Atmos 65L last week and I'm now shopping for tents.
The one I'm looking at is the Quarter Dome SL 2 which is lightweight and the perfect size for me + my kid.
My question is, would this tent fit in my backpack?
I have the Half Dome version of that tent and a Gregory 65L pack. The tent fits into it with ease, along with my larger sleeping bag and everything else.
The trick is to take the tent, fly, and footprint out of the stuff sack and cram it (carefully) into the bottom of your pack.
one point to note is that the QD SL2 is semi-freestanding which means the tent body is not fully supported by the pole system. You have to stake out the two corners of the foot end which is slightly more annoying to set up than a freestanding tent where the body is fully supported.
You typically have to stake out the vestibules of the fly on most free standing tents and you should always stake/guy out a tent to stop if from blowing away.
one little caveat, frame of reference here is 'summer backpacking'. If you need to stuff in a bear vault or larger winter bag/mat, you'll probably need to start stuffing those outer pockets.
I would also say you'll have no problem. I have a Gregory 65L and have also had the REI Quarter Dome 2 (older version) on trail with me. I never had any issues fitting that and everything else in there.
Shouldnt be a problem. Worst case, put the poles on the outside in the side pocket and under the compression strap. Sometimes poles dont want to pack nicely. You can put a lot into a 65L pack. Just remember, you dont HAVE to fill it. They carry ok without being stuffed.