Here's an interesting article that I found:
http://www.sportsnola.com/sports/sports-blogs/rene-nadeau/585378-size-matters-sometimes-a-look-at-college-footballs-offensive-lines.html
It looks like the trend of the big O-linemen has been reversing, albeit not by very much.
And I quote:
"So, you think that athletes are getting bigger, stronger and faster. Well, part of that statement is a misconception, of sort.
Players competing to excel in all sports are certainly showing the results that would indicate that today's athlete is faster and stronger than their predecessors. But the bigger part? Actually, the average size of college football offensive linemen is shrinking.
About five seasons ago, the average O-lineman in college football was a little over 304 pounds per man. Back in the late '90's, the standard size was in the 307 pound range.
....
The average starter in college football in 2012 is 302.8 lbs. per man.
...
I know what you're wondering. What does this all mean and which teams (and conferences) are the biggest today? Well, here are the facts.
The SEC is the heaviest conference on the O-line per team with an average weight of 307.54 lbs. per team (averaged 8 wins per team in 2011, 2nd most of any conference)
The ACC is 2nd with a 305.15 average (averaged 6.5 wins per team last season)
The Big 12 303.58 lbs.(averaged 8.4 wins per team last season, most of any conference)
The Big Ten with a 301.5 average (with 7.3 wins per team in 2011)
The Big East 300.5 lbs. (7 wins per member in 2011)
Sun Belt 300.2 lbs. (5.5 wins per team)
PAC Ten 299.95 lbs. (6.75 wins per team)
Conference USA 299.43 lbs. average.(6.1 wins per team)
Mid American 299.27 lbs. (5.6 wins per team)
Western Athletic 293.57 lbs. (5.1 wins in 2011)
Mountain West 293.4 lbs. (5.8 wins per team last fall)
Independents 289.3 (including Army and Navy; 6.5 wins per member)."