Hi Jesse,

Here are our resources related to the Farm Direct Marketing laws and regulations. 

I highly recommend that you reach out to Oregon Department of Ag directly to confirm your understanding and to see if they have any mushroom specific considerations. 

ODA Food Safety 
635 Capitol St NE Salem, OR 97301 
Phone: <personal data hidden>
Email: <personal data hidden>

Your license needs kick in when you want to sell beyond farm direct, for example to retail locations and once you start processing for value add. https://www.oregon.gov/oda/programs/foodsafety/fslicensing/pages/retail.aspx

Please see text below for Value Add considerations. 
 
Legal Guide to Farm Direct Marketing https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/pnw680.pdf

Keeping it Legal https://industry.traveloregon.com/wp-content/uploads/2017/03/03_RegulationsLicensesforSellingandGrowingFoodinOregon.pdf

Regulations for Selling Fresh Cultivated Mushrooms
There are relatively few regulations for selling
conventionally grown mushrooms. The Food Safety
Modernization Act (FSMA) Produce Safety Rule
establishes some requirements for selling fresh
cultivated mushrooms. Producers making value-added
products such as a ready-to-eat (RTE), processed
(e.g. mechanical drying, slicing, canning, or freezing)
or RTE packaged mushroom products must meet
food processing requirements.

REGULATIONS FOR SPECIFIC PRODUCTS SELLING MUSHROOMS
FSMA Produce Safety Rule
The FSMA Produce Safety Rule applies to mushroom
growers and sets requirements for controlling potential
food safety hazards on the farm. The scale of a farm
and type of customers a farm sells to determine
the specific compliance expectations. The Produce
Safety Rule includes requirements for compost and
other inputs of animal origin, such as manure. These
requirements apply to mushroom substrate. The rule
also specifically requires that raw mushrooms must
be packed in a manner that prevents the formation
of Clostridium botulinum toxin. Reducing the risk
of Salmonella and Listeria, along with other human
pathogens, is also especially important for mushroom
producers.

The FSMA requirements for mushroom growers
are very similar to the standards established in the
Mushroom Good Agricultural Practices (MGAP). The
Penn State Extension website, extension.psu.edu, is a
good source for food safety resources for mushroom
growers and processors.

For more information for farms about exemptions and
requirements in the Produce Safety Rule, please see
the “FAQ on the Food Safety Modernization Act” fact
sheet. https://www.fda.gov/food/food-safety-modernization-act-fsma/frequently-asked-questions-fsma

Beyond any FSMA requirements, no special
inspection or license is needed to sell fresh cultivated
mushrooms in their natural state as a raw agricultural
product.

Mushrooms are commonly sold loose in bulk by
weight. Raw bulk mushrooms may be sold to end
consumers in a variety of container types and sizes,
including baskets and trays, without a WSDA Food
Processor License. It should be clear to customers
that the product is not ready to eat. A statement on
the package or nearby to “wash before eating” or
something similar can help avoid confusion.

HANDBOOK for SMALL AND DIRECT MARKETING FARMS 2019
Selling Processed Mushrooms
Value-added products, including sliced dried
mushrooms, mushroom powders, teas, and tinctures
or extracts, are all products that must be made with
a Food Processor License and facility. https://www.oregon.gov/oda/programs/foodsafety/fslicensing/pages/processingwarehouse.aspx This includes:
• Mushrooms that are packaged and presented for
sale as “ready to eat.”
• Mushrooms that are mechanically dried (e.g.,
with fans or heating) for use in food or products
that will be ingested (e.g., seasonings, teas,
supplements). Air-drying without any mechanical
fans or heat does not require a Food Processor
License, when not otherwise processed.
• Mushrooms that are sliced, dried, powdered,
pressed, extracted, distilled, frozen, or otherwise
transformed into food or products that will be
ingested.

This is a lot of information that will give you an idea of where to start, but ODA Food Safety Department will be your best point of contact for updated regulations and recommendations with selling mushrooms.