What are good alternatives when Obsidian trailhead permits are sold out?

Work the rest of the Central Cascades permit system, because every limited-entry trailhead carries its own quota and demand varies sharply between them. When Obsidian is gone for your date, several comparable trailheads in the same wilderness complex are worth checking immediately.

The strongest substitutes by demand and character: Green Lakes/Soda Creek, which delivers the classic South Sister and Broken Top alpine scenery; Tam McArthur Rim, with its high viewpoint plateau; and Jack Lake for Canyon Creek Meadows, the wildflower alternative. Pamelia Lake and Marion Lake serve the Mount Jefferson end of the system for a quieter version of the same forest-to-alpine day. All of these sit one demand notch below Obsidian and Devils Lake/South Sister, which in practice means dates survive noticeably longer.

Two system-level tactics also help. First, weekdays: quota pressure across the whole Central Cascades system concentrates on Saturdays, and a Wednesday Obsidian permit is often available when the weekend is long gone. Second, cancellations: reserved day-use permits get returned steadily as plans change, and the popular trailheads are exactly where those returns are worth watching for right up to your date.

If your trip is overnight rather than day-use, remember the overnight permit is a separate product for the wilderness, so check that inventory rather than the day-use calendar before assuming the weekend is lost.