Mass of the pendulum does not have any effect on the number (or amount) of times it will oscillate in a given time duration. The number of times a bob will oscillate is known as its frequency and is calculated as the inverse of time period of the bob. The time period of the pendulum is mathematically given as:
`T = 2pi sqrt(L/g)`
where, T is the time period of pendulum, L is length of the pendulum (distance from the fixed point) and g is acceleration due to gravity.
Hence, the amount or number of times a pendulum will oscillate (i.e., its frequency) will be given as:
`f = 1/T = (1/(2pi))sqrt(g/L)`
A pendulum when released from position of rest oscillates due to the pull exerted by the earth's gravity. And it has no relation to the mass of the pendulum and hence a 2 lb ball will have the same frequency as a 200 lb wrecking ball, provided the same length.
Hope this helps.