I've done it many times over the years without a problem. Oxidation in the fermenter isn't a concern until fermentation is completely finished. Yeast consumes available oxygen during active fermentation, and will easily take care of any oxygen even if the headspace is a few times larger than the volume of fermenting beer.
And while we're at it - it is generally best to minimize oxygen exposure whenever practical, but a bit of oxidation isn't normally going to make a batch of beer undrinkably bad even if it does happen.