Complex sentence: Oregon's biggest producer produces only 125,000 cases per year, most produce under 35,000 cases, and the state features many small wineries which produce less than 5,000 cases per year.
Split into simpler sentences: Oregon's biggest producer produces only 125,000 cases per year and most produce under 35,000 cases. The state features many small wineries which produce less than 5,000 cases per year.