Hello, ChirsBush. Oakleaf hydrangeas should be peeling their bark in your area about now or so. Mine have just about completed that and are putting out new foliage growth on top of last year's leaves. You can just let the bark peel and fall to the ground on its own whenever it wants to.
In the Spring, hydrangeas also begin to make internal changes to the stems and branches to basically 'turn off' the winter protection that protected the flower buds and the various stems/branches thru winter. At this time, you may notice that the surface color changes from sandy or grayish to greenish. In the Fall, as they harden for winter, the stems turn sandy/grayish. This is all normal.
However, oakleaf hydrangeas should not be pruned when they did or normally. Tell the landscapers to keep these hydrangeas off limits (unless you first 'ok') and to, normally, never to do this at this time because the result is that now, you will not get flowers this year. Oakleaf hydrangeas typically develop invisible flower buds at the ends of the branches in the Summer/Fall and then these invisible flower buds open in Spring. Because of the pruning, there are no flower buds in the shrubs now so this year, you will just get new stems, new branches and new foliage. The invisible flower buds develop somewhere from July thru September, depending where one is located. For me that happens in mid July-ish and later for you up north. If you want, make an electronic reminder for 2019 and set it to display before you normally engage the landscape people or before you yourself start pruning, whichever happens first. Or make a note in a wall calendar and pass it on into 2019's calendar in December 2018 (when you buy the 2019 calendars).
Hydrangeas normally do not need to be pruned on a regular basis if they have been planted in an area where they can attain their estimated size at maturity per the plant label. If the shrub was already in the house when you bought it, you can research the type of oakleaf hydrangea and then look what estimated heights and widths are given online by mail order companies or by universities. Some get large 10' say and others are more compact (Ruby Slippers, Muchkin, Pee Wee, Sikes Dwarf, Jetstream, Vaughn's Lillie). The only prunings that I would do to oakleafs is (a) in mid-to-late May, I would prune to the ground any stems that have not leafed out (hardly happens for me) or (b) prune any growth that might be a safety issue (growing into walking surfaces, etc). Oakleafs can be safely pruned any time after they have bloomed but before this July-September period when they develop the invisible flower buds.
The good news is that this pruning will not affect the gorgeous Fall foliage that they produce so enjoy that! Hope that helps.