A quarter is another way of saying one fourth, in this setting, one fourth of a year = three months. Quarterly means something that happens every 3 months. Edit
Outfielder Ty Cobb, whose career ended in 1928, has the highest batting average in Major League Baseball (MLB) history. He batted .366 over 24 seasons, mostly with the Detroit Tigers. In addition, he won a record 11 batting titles for leading the American League in BA over the course of an entire season.
Mark Whiten, for example, tied Jim Bottomley for the most runs batted in in a single game with 12 in his four-homer game. Shawn Green hit a double and a single along with his four home runs for 19 total bases, an MLB record. It surpassed Joe Adcock's mark of 18, which also came from a four-homer game.