My 1965 Sourcebook On The Space Sciences indicates that they are resolvable:
The polar flattening of [Uranus] is clear from its telescopic image and the ellipticity determined from the motion of the nearest satellite is 1/18. The result derived from direct measurement of the equatorial and polar diameters is about 1/12, but since the maximum angular diameter of Uranus as seen from Earth is only 4 sec of arc, it is evident that this value of the ellipticity cannot be very accurate...
In the telescope, Uranus is seen as a somewhat flattened spherical body with a greenish color... at certain times a whitish equatorial zone and other bands, similar to but fainter than those of Jupiter and Saturn, can be observed.
Like Uranus... Neptune has a greenish color... Observers have occasionally reported seeing faint irregular markings and a bright equatorial zone on Neptune, but the situation is uncertain.
However, there are no photos of either in the book, unlike Jupiter and Saturn, which both have fairly detailed mid-century photos from Hale-Palomar.
The 1964 English translation edition of Flammarion Book Of Astronomy has photos of Uranus from 1936! A very small disc is visible, with no evident features. No photos of Neptune are in the book, possibly because it would show merely a point.
Interestingly, the book has a variety of pictures of Jupiter and Saturn from the 1910s through the 1950s, from different observatories (Flammarion, Lowell). Remarkably, they all show comparable levels of detail in Jupiter, with the main difference, as far as I can tell, being the quality of the photographic film grain.