December 1, 8, 15: Tuesday Quads begin. Typically, this is a 3-round round robin, with players sorted by ratings. However, December, with its 5 Tuesdays, offers the possibilities of additional games, so a different format may occur, depending on the number of players and their wishes. Chess.com rated.
December 3, 10, & 17: Thursday Game in 15. Play 3 games in an evening–try out different openings. Chess.com rated.
December 5 & 6: PCC Winter Open Online. This is a 4-round Swiss in 3 sections, so you will play others in a similar rating range. USCF Chess membership required.
December 19: Third Saturday Blitz.
See www.pdxchess.org for more information.