Quidditch is big at Hogwarts. Each house fields a team, which includes the seven players and often one or two reserve players as well. The teams have a team captain who not only plays but also acts as coach. The captain leads practices, devises strategies, and sees to the induction of new players into the team.Quidditch tryouts are during the second week of the school year; students who wish to play for their house are asked to talk to Madam Hooch. The Quidditch season at Hogwarts starts in October, with the first games early in November. Madam Hooch is the resident Quidditch expert. The Bludgers, Quaffles, and Snitch are stored securely in her office between games and she acts as referee for the matches. Team practices are scheduled by individual captains (they "book the field" to reserve it for their own team to practice.) Most teams practice almost every day, after school or in the evenings. 

The matches themselves are well attended by almost everyone in the school. The commentary is provided by Lee Jordan, a Gryffindor boy who occasionally finds it difficult to remain objective when Gryffindor is playing Slytherin. The raised stands can hold hundreds of fans, and it would seem that the matches are sometimes attended by Quidditch fans from the surrounding area as well.

The team which wins the most matches each year is awarded the Quidditch Cup, a great honor. Special awards are given to the best players as well (SS/f).

Each year, the various House teams play each other [1]. This results in six games of Quidditch:
Gryffindor V. Slytherin
Gryffindor V. Hufflepuff
Gryffindor V. Ravenclaw
Hufflepuff V. Slytherin
Hufflepuff V. Ravenclaw
Ravenclaw V. Slytherin

Thoughts on Quidditch at Hogwarts
essay by Patrick Drazen

Each House has fourteen players, Second-Year and up (an exception being made in Harry Potter's case).  Quidditch being such a physical contact sport, players tend to suffer everything from bumps and bruises to broken bones.  Hence, there is a necessity for a Reserve squad to step in if a player becomes incapacitated.  Otherwise, the team would have to forfeit the match.  There is also a need for a healer at Hogwarts, where Madam Poppy Pomfrey runs the Hospital Wing.

Of course, if the students had their way, there would probably be Quidditch every other weekend, and a colossal amount of skiving-off of homework and studying.
 

• Atlas of Hogwarts: The Quidditch Pitch
• Gryffindor
• Slytherin
• Hufflepuff
• Ravenclaw
• games and players of years gone by

Gryffindor
robes: scarlet
Gryffindor traditionally fields a strong team, although they lost the cup to Slytherin for seven years between 1985 and 1991, ever since the great Charlie Weasley was Seeker for the team. With the addition of Harry Potter as Seeker in 1991, at the time the youngest House player in over a hundred years, the Gryffindor team was widely believed to be the best team at Hogwarts. Unfortunately, the team lost their chance for the cup in spring 1992 because Harry was out of action for the final game and again in spring 1993 when the competition was cancelled. In 1994, finally, Gryffindor took their well-deserved victory and won the cup. The captain for Gryffindor was Oliver Wood, a strong and very capable player who played Keeper in Harry's first three years. Wood was obsessive about the game, dragging his team out for more practices than any other team and devising complicated strategies over the summer to inflict on his players in the fall. 

• Katie Bell - Chaser
• Angelina Johnson - Chaser
• Harry Potter - Seeker
• James Potter - Chaser (1970s)
• Alicia Spinnet - Chaser
• Fred Weasley - Beater
• George Weasley - Beater
• Oliver Wood - Keeper (captain) (1991-1993)
• Charlie Weasley - Seeker (1980s)

• Bletchley - Keeper (1991)
• Bole - Beater (1993)
• Derrick - Beater (1993)
• Marcus Flint - Chaser (captain)
• Terence Higgs - Seeker (1991)
• Draco Malfoy - Seeker (1992, ff.)
• Montague - Chaser (1993)
• Adrian Pucey - Chaser (1991)
• Warrington - Chaser (1993)

• Cedric Diggory - Seeker

• Cho Chang - Seeker
• Roger Davies - (captain)

games and players of years gone by
 

• Awards have been given for Quidditch for many, many years at Hogwarts. 
• The last time a first year student was allowed onto one of the house teams was over a hundred years ago. 
• A plaque in the Trophy Room (film only, this information is not correct according to comments the author has made) shows the following names and information:
• R. J. H. King won an award for Gryffindor in 1969.
• M. G. McGonagall (not the professor, who was a teacher at that time) won an award in 1971
• James Potter won a Seeker award for Gryffindor in 1973.
• Charlie Weasley is considered to be one of the best players in recent memory. He played for Gryffindor in the mid-80s.

[1] Evidence from books one and three support this.  In book one, Harry Potter an the Sorceror's Stone, both the Gryffindor V. Slytherin game and the Gryffindor V. Hufflepuff game are descirbed in detail (Chapters Eleven and Thirteen).  Then Ms. Rowling clearly states in Chapter Seventeen that Gryffindor played and lost a match to Ravenclaw, since Harry was unconscious at the time.  In book three, Harry Potter and the Prisoner of Azkaban, the Gryffindor matches are all three described.  In Chapter Nine, Gryffindor's loss to Hufflepuff is told.  Chapter Thirteen is entitled Gryffindor Versus Ravenclaw.  And Chapter ifteen, entitled The Quidditch Final, Gryffindor is vitorious over Slytherin, winning them the Quidditch Cup.  Matches between other houses are alluded to in this exchange in Chapter Nine of The Prisoner of Azkaban:

"It's not over yet," said Fred.  "We lost by a hundred points, right?  So if Hufflepuff loses to Ravenclaw and we beat Ravenclaw and Slytherin..."
"Hufflepuff'll have to lose by at least two hundred points," said George.
"But if they beat Ravenclaw..."
"No way.  Ravenclaw is too good.  But if Slytherin loses against Hufflepuff..."