The Bay Area Ridge Trail is especially scenic at this time of year. Not all parts are dog-friendly, unfortunately, and some entry points will require you to clamber up steep slopes to get to the ridge trail itself (which, depending on your point of view, can be a good or a bad thing...).
If you're looking for an easy but rewarding fall hike, we've got a suggestion. The East Ridge Trail in Redwood Regional Park, easily accessed from the Skyline Staging Area off Skyline Blvd. in Oakland, puts you conveniently at the top of the ridge and lets you walk along for mile after scenic mile with a minimum of huffing and puffing and a maximum of amazing vistas, with pines, oaks, eucalyptus and redwoods in fragrant combinations.
For a moderate loop, we heartily recommend turning around at the Phillips Loop marker (about one mile out), which will drop you onto a path through a more wooded valley and return you to a spot near the trailhead. One caveat: especially in the late summer and fall, you will probably want to leash up as you go this way, as the poison oak is growing in lush profusion in many areas where an off-leash dog is likely to go exploring. Besides, some of the local snakes along the path may be too enticing for their own good.