Based on the latest studies and research, here are my short and longer answers.

Short Answer
Drinking a protein shake as close to the end of your weight lifting workout as possible does absolutely no harm and depending on three other factors may be beneficial to your muscular development.  Therefore I do recommend consuming a protein shake after your weightlifting workout as you have nothing to lose and potentially a lot (of muscle) to gain.

The Longer Answer
Based on the latest studies that I am aware of the scientific community is in agreement that there are two primary factors, and one secondary factor, which will influence how beneficial a post workout protein shake will be on your muscular development.

Primary Factor #1
The first and most important factor is your total daily protein intake.  If you are meeting your daily protein requirements the effects of a post workout protein shake have been found to be minimal.  However if you are not meeting your daily protein requirements a post workout protein shake has been found to be beneficial to muscular development.

However, the prevailing reasoning is that a post workout protein shake is beneficial not due to its timing, but rather that the shake is adding much needed protein to your already deficient total daily protein intake.

*Remember, the harder you are training and the more muscle mass you already have the higher your daily protein requirements.

Primary Factor #2

The second factor that influences how beneficial a post workout protein shake may be is the timing between when you last ate and when you work out.

Assuming you are meeting your total daily protein needs…

If you haven’t eaten within 6 hours before your workout, studies have shown that a post workout protein shake will have at best a moderately beneficial impact on muscular development.

If you have eaten 4-6 hours before your workout, studies have shown that a post workout protein shake will have at best a somewhat, but minimally beneficial impact on muscular development.

If you have eaten between 2-4 hours before your workout, studies have shown a post workout protein shake will have a slight, if any, beneficial impact on muscular development.

If you have eaten within 2 hours before your workout, studies have shown a post workout protein shake will have no benefit on muscular development.

It is hypothesized that this is the case since a meal eaten within 2 hours of a workout which contains ample high quality protein will indeed provide your body with enough raw materials it requires to optimally recover, repair, and grow after a workout.

Secondary Factor

Your training history, goals, current routine and current physique will influence how beneficial a post workout protein shake will be.

The longer you have been training, the harder you are training, the more aggressive your goals are and the more muscle mass you already have, the higher your daily protein requirements will be and the more precise your meal timing needs to be.

Consequently a post workout protein shake will be more beneficial for harder training individuals than for those with more moderate goals.

In essence, it gets harder and harder to make performance and physique gains as we progress thus it becomes more important to take advantage of every possible method to maximize ones progress.

Conclusion

There is absolutely no harm in consuming a post exercise protein shake and depending on your total daily protein intake, how long before your workout you last ate, and how hard you are training, how long you have been training, your goals, and your current physique, a post workout protein shake may be quite beneficial to your muscular development.

To Our Health,

Zach