Here ins the U.S., the Cottontail Rabbit, in a few minimally different varieties, reaches maturity at about 6 to 8 weeks. They can grow, depending on many factors, to about 2 to 3 pounds in size. At around the 6 to 8 weeks age they can be hunted and eaten. We also have hares... usually just two sub-species; the western Jackrabbit and the Snowshoe Hare. Boths are considerably larger than the Cottontail, but in the case of the Jackrabbit, decidedly unedible, in my opinion (after several ill-informed attempts). They both reach maturity, however, in the same 6 to 8 week time range.
You knew, of course, that a wild rabbit can produce nearly 40 offspring each year... so eat up!