Sequoia Lodge is operated by the City of Oakland
Sequoia Lodge sounds like it might fit the bill. It's a city of Oakland property and you can self cater (there is a kitchen onsite). There is outdoor space, and I've been to events there with enough room for a DJ and dancing without being so overwhelmingly large that the space would look empty with 50 people.
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Check out the Oakland Parks Dept. Sequoia Lodge is a great party/dance place. They have a ''sunken'' sitting area with a big fireplace.
My husband & I got married at the Sequoia Lodge in the Oakland hills. It's run by Oakland Parks & Rec. It's a beautiful lodge with full facilities; we had 80 guests, catering, a DJ with dancing, and full seating with tables, and the room could have held more. The price was reasonable at the time, but I don't know what it is now. Give them a call for a price and a look-see. andrea