Golf balls consisting of a core and a cover are disclosed. The core is a solid, single-layer core formed from a rubber composition comprising a base rubber, a free radical initiator, and a hydroquinone. A ratio of the amount of the hydroquinone present in the rubber composition, measured in parts by weight, to the amount of free radical initiator present in the rubber composition, measured in parts by weight, is generally from 0.05 to 2. The core has a positive hardness gradient such that the difference between the core's surface hardness and the core's center hardness is 25 Shore C units or greater and/or the core has a diameter of from 1.51 inches to 1.59 inches.