A shot from the side would be a little better for id purposes, however it looks like Heteroecus pacificus to me. 1) The oak is Quercus chrysolepis, which narrows down the possibilities in terms of what galls might be present. (Based on the underside of one leaf visible in the image, I'm pretty sure this is Q. chrysolepis.) 2) The somewhat spindle shape and the lack of hair/fuzz point to Heteroecus pacificus.

Colors of Heteroecus pacificus galls vary. The shape can vary too, depending on the presence of inquilines or parasitoids in the gall (both of which are very common).

Moved from Gall Wasps.

Moved from Unidentified Galls.