Plant them in the ground now. About pruning? you can do that simultaneously when you plant out. In fact if you lessen the foliage the more energy it would channel to its roots.

Euonymous are pretty hardy and vigerous growers. They could have been planted out in the ground a long time ago. In fact, that's why they have hit a plateau in their growth. There is only so many nutrients available in the soil in a pot and eventually the plants use it up. They will take off like gangbusters once you plant them. You don't say where you've been keeping them....if they've been in a greenhouse or a sheltered spot, make sure you "harden them off" before sticking them out in full sun and weather. Put them in some light shade outdoors at first and then over the course of a week or two, bring them out into full sun and wind, rain etc. No need to prune at this point unless they have the odd stray branch that especially sticks out and you want to keep them a uniform size.

Thank you for such valuable info. They've been in little pots in a south window in the house since last summer. I will definitely harden then off on the back deck for a few days, and get them in the ground. I will be so excited to see them growing. Almost as excited I was to see them forming roots just from the clippings from my neighbors shrub! It's such a nice variety - dark leaves, blooms white, and quite a large shrub that climbs up the chain link fence in behind the house. I couldn't find this type in garden centres around me. So I'm excited to get these babies in the ground this year.

Water them well and keep them moist while they are undergoing the added stress of being outdoors. The leaves will be tender from always being indoors and could easily burn from sun and wind. Ease them gentley into harsher conditions. You've got them this far! Another week or two before planting out won't hurt them. Good luck!

ah.. next time when doing cuttings, leave them outdoors even in winter. Just place them in a protected spot. They do not need to be overwintered indoors. The way I go about propagating cuttings is to start in late spring and just set them in a cold frame until I can safely plant them out the following year. Euonymous though are more easily propagated by root layering. Just take a semi green branch attached to a mother plant and pin it down to the ground. It will root naturally. Or do air layering. just scrape off a bark by a leaf node, encase that area with sphagnum moss and wrap in a perforated plastic. By next season, it would be fully rooted and you'd probably get a bigger plant by this method.

as for pruning - yes I would for young plants when you'd like to start shaping them into fuller plants.