Museum Tegernseer Tal is the valley's local history museum, housed in the old vicarage opposite the former monastery. Its rooms cover the culture of old Bavaria around the lake: religious objects, household tools, crafts, costumes, paintings, and bits of everyday life from the 14th to the 20th centuries.
It is a small museum, but useful before or after seeing St Quirinus. Tegernsee can feel like a polished resort; this museum gives the place a deeper rural and monastic backstory.