'serving as a cornerstone' is a perfectly correct and usable phrase in written English.
It is often used to signify something that is fundamental or essential. For example, "Education is a critical part of any society, serving as a cornerstone which helps us progress and develop."
That portrait served as a cornerstone for later acquisitions in the field, particularly over the last 20 years.
The portrait served as a cornerstone for later acquisitions in the field.
The defendant's words served as a cornerstone of his defense, which has called a handful of witnesses.
The advisory could serve as a cornerstone of the "positive training" method endorsed by so many dog professionals.
The preamble has served as a cornerstone or the bedrock of what is expected of a NATO member.
The portrait served as a cornerstone for later acquisitions in the field, particularly over the last 20 years.
deal would serve as a cornerstone for Argentina's renegotiation of the debt it defaulted on last year.
More than a century has come and gone since Wallace released this groundbreaking work, yet his map largely still serves as a cornerstone for understanding modern distributions of biodiversity.
For its part, Israel's defense minister, Ehud Barak, issued a rare statement of regret, signaling just how important Israel sees preserving the peace with Egypt, which has served as a cornerstone of its regional policy for decades.
Similar to how the US Constitution is seen as a living document with interpretations that have expanded over the years, more so is the Quran, which serves as a cornerstone of Shariah, he said.
According to the 2005 Dietary Guidelines for Americans, fruits and vegetables serve as a cornerstone of a healthful diet, yet calorie for calorie, they are far more expensive than foods high in added fats and sugars.
